quence.lua

-- QUENCE: sequencer
-- v2.2.8 @spunoza
-- llllllll.co/t/29436

-- Q * U * E * N * C * E
--
-- a probababilistic
-- 4-track sequencer
-- for norns and grid
-- with output for MIDI
-- and Molly the Poly
-- and crow
--
-- by Rob Schoen
-- millxing at gmail
-- https://llllllll.co/u/spunoza/summary
-- https://github.com/millxing/QUENCE
--
-- inspired by
--  Turing Machine,
--  Fugue Machine,
--  and Physical (Norns Study 4)
--
-- random tips:
-- bottom row's always the
--  toolbar: pause, mutes for
--  tracks 1-4, lock all,
--  clear all, select tracks
--  1-4, and select settings
--  page.
-- hold button 3 to see the
--  midi notes in the sequence
--  for the current track
-- on the settings page, the
--  eight buttons in rows 5-6,
--  cols 13-16 are currently
--  unassigned, but for now you
--  can hit any of them to
--  resync all of the sequences
--
-- updated for norns 2.0
-- + molly_the_poly output
-- by _ground_state_
-- https://llllllll.co/u/ground_state/summary
--
-- updated for crow and just friends
-- by justmat
-- https://llllllll.co/u/justmat/summary

engine.name = 'MollyThePoly'
local music = require 'musicutil'
local beatclock = require 'beatclock'
local MollyThePoly = require 'molly_the_poly/lib/molly_the_poly_engine'
local options = {}
options.OUTPUT1 = {'midi', 'audio', 'midi + audio', 'crow jf', 'crow cv 1/2', 'crow cv 3/4'}
options.OUTPUT2 = {'midi', 'audio', 'midi + audio', 'crow jf', 'crow cv 1/2', 'crow cv 3/4'}
options.OUTPUT3 = {'midi', 'audio', 'midi + audio', 'crow jf', 'crow cv 1/2', 'crow cv 3/4'}
options.OUTPUT4 = {'midi', 'audio', 'midi + audio', 'crow jf', 'crow cv 1/2', 'crow cv 3/4'}

-- declare variables
local position = {}
local tempomod = {}
local seqlen = {}
local dispersion = {}
local press = 0
local transpose = 0
local page = 0
local tpage = 0
local pagecopy = 0
local lock = 0
local pause = 1
local tick = 0
local tonicnum = 0
local toniclist = {}
local changelist = {}
local rflist = {}
local change = {}
local restfreq = {}
local mnote = {}
local mute = {}
local maxscreen = 0
local maxgrid = 0
local inact = 0
local mode = 0
local center = 0
local scale = {}
local tempo = 0
local steps = {}
local rests = {}
local steps_copy = {}
local rests_copy = {}
local clk = beatclock.new()
local trackout = ' '
local pxcurve1 = 0
local pxcurve2 = 0
local play_mode = {0, 0, 0, 0}
local reverse_play = {false, false, false, false}
local pingpong = {false, false, false, false}

-- connect grid
local grid_device = grid.connect()

-- midi code
local midi_device = midi.connect()

-- set up just friends
local function setup_jf()
    if params:get('output1') == 4
            or params:get('output2') == 4
            or params:get('output3') == 4
            or params:get('output4') == 4 then
        crow.ii.pullup(true)
        crow.ii.jf.mode(1)
    else
        crow.ii.pullup(false)
        crow.ii.jf.mode(0)
    end
    end

-- set up crow cv outs
local function setup_crow_cv()
    crow.output[2].action = "{to(5,0),to(0,0.25)}"
    crow.output[4].action = "{to(5,0),to(0,0.25)}"
end

local function p_mode_to_char(track)
    local chars = {'->', '<-', '<>'}
    return chars[play_mode[track] + 1]
end

function init()
    grid_device:rotation(0)
    opening_animation()
    math.randomseed(os.time())
    for knob = 2, 3 do
        norns.enc.accel(knob, false)
        norns.enc.sens(knob, 3)
    end

    -- initalize variables
    for track = 1, 4 do
        position[track] = 0
        tempomod[track] = 1
        seqlen[track] = 16
        dispersion[track] = 5
    end
    page = 1
    tpage = -99
    pagecopy = 1
    pause = 1
    toniclist = {'C', 'C#', 'D', 'D#', 'E', 'F', 'F#', 'G', 'G#', 'A', 'A#', 'B'}
    tonicnum = 1

    -- probabilities for randomness and rest frequencies
    pxcurve1 = 1.5
    changelist = {
        0,
        (1 / 6) ^ pxcurve1,
        (2 / 6) ^ pxcurve1,
        (3 / 6) ^ pxcurve1,
        (4 / 6) ^ pxcurve1,
        (5 / 6) ^ pxcurve1,
        1.00,
    }

    pxcurve2 = 1.5
    rflist = {
        0,
        (1 / 6) ^ pxcurve2,
        (2 / 6) ^ pxcurve2,
        (3 / 6) ^ pxcurve2,
        (4 / 6) ^ pxcurve2,
        (5 / 6) ^ pxcurve2,
        1,
    }

    -- set defaults
    change = {7, 1, 1, 1}
    restfreq = {1, 1, 1, 1}
    mnote = {0, 0, 0, 0}
    mute = {0, 0, 0, 0}

    -- norns and grid parameters
    maxscreen = 6
    maxgrid = 10
    inact = 4

    -- set up musical scale
    mode = 13 -- default = minor pentatonic
    center = 48 + (tonicnum - 1) -- tonic center
    scale = music.generate_scale_of_length(center - 12, music.SCALES[mode].name, 24)
    tempo = 60 -- default tempo

    -- initalize sequences
    for track = 1, 4 do
        steps[track] = {}
        rests[track] = {}
        for step = 1, seqlen[track] do
            steps[track][step] = 15
            rests[track][step] = 1
            steps_copy[step] = steps[1][step]
            rests_copy[step] = rests[1][step]
        end
    end
    params:add{
        type = 'option',
        id = 'output1',
        name = 'output1',
        options = options.OUTPUT1,
        action = function()
            clear_all_notes()
            if params:get('output1') == 4 then setup_jf() end
            if params:get('output1') == 5
                or params:get('output1') == 6 then setup_crow_cv() end
        end,
    }
    params:add{
        type = 'option',
        id = 'output2',
        name = 'output2',
        options = options.OUTPUT2,
        action = function()
            clear_all_notes()
            if params:get('output2') == 4 then setup_jf() end
            if params:get('output2') == 5
                or params:get('output1') == 6 then setup_crow_cv() end
        end,
    }
    params:add{
        type = 'option',
        id = 'output3',
        name = 'output3',
        options = options.OUTPUT3,
        action = function()
            clear_all_notes()
            if params:get('output3') == 4 then setup_jf() end
            if params:get('output3') == 5
                or params:get('output1') == 6 then setup_crow_cv() end
        end,
    }
    params:add{
        type = 'option',
        id = 'output4',
        name = 'output4',
        options = options.OUTPUT4,
        action = function()
            clear_all_notes()
            if params:get('output4') == 4 then setup_jf() end
            if params:get('output4') == 5
                or params:get('output1') == 6 then setup_crow_cv() end
        end,
    }
    params:add_separator()
    params:add{
        type = 'option',
        id = 'rotation',
        name = 'grid rotation',
        -- really doesn't make sense to offer all four options here
        options = {'0', '180'},
        default = 1,
        action = function(value)
            -- hack
            if value == 1 then
                value = 0
            end
            -- grid API expects [0-3]
            grid_device:rotation(value)
            grid_redraw()
        end,
    }

    -- clock settings
    local clk_midi
    clk_midi = midi.connect()
    clk_midi.event = clk.process_midi
    clk.on_step = count
    clk.on_select_internal = function() end
    clk.on_select_external = function() end
    clk:add_clock_params()
    params:set('bpm', tempo)
    params:add_separator()
    MollyThePoly.add_params()
    redraw()
    grid_redraw()
    params:default()
end

local function screen_write(row, col, printable, level)
    screen.level(level)
    screen.move(row, col)
    screen.text(printable)
end

-- redraw screen
function redraw()
    local bright = maxscreen - 4
    screen.clear()
    screen_write(0, 10, 'global bpm: ', maxscreen)
    screen_write(50, 10, params:get('bpm'), bright)
    screen_write(92, 10, 'tonic: ', maxscreen)
    screen_write(118, 10, toniclist[tonicnum], bright)
    screen_write(0, 20, 'scale: ', maxscreen)
    screen_write(27, 20, music.SCALES[mode].name, bright)
    screen_write(0, 30, 'sequence lengths: ', maxscreen)
    screen_write(80, 30, seqlen[1] .. ' ' .. seqlen[2] .. ' '
                    .. seqlen[3] .. ' ' .. seqlen[4], bright)
    screen_write(0, 40, 'tempo modifiers: ', maxscreen)
    screen_write(73, 40, tempomod[1] .. ' ' .. tempomod[2] .. ' '
                    .. tempomod[3] .. ' ' .. tempomod[4], bright)
    screen_write(0, 50, 'dispersions: ', maxscreen)
    screen_write(54, 50, dispersion[1] .. ' ' .. dispersion[2] .. ' '
                    .. dispersion[3] .. ' ' .. dispersion[4], bright)
    screen_write(0, 60, 'play mode: ', maxscreen)
    screen_write(48, 60, p_mode_to_char(1), bright)
    screen_write(56, 60, ' | ', maxscreen)
    screen_write(65, 60, p_mode_to_char(2), bright)
    screen_write(72, 60, ' | ', maxscreen)
    screen_write(81, 60, p_mode_to_char(3), bright)
    screen_write(88, 60, ' | ', maxscreen)
    screen_write(97, 60, p_mode_to_char(4), bright)
    screen.update()
end

-- redraw grid
function grid_redraw()
    if tpage ~= page then
        grid_device:all(0)
        grid_redraw_ctrl()
    end
    if page == 0 and tpage ~= page then
        grid_redraw_home()
    end
    if page > 0 then
        grid_redraw_page()
    end
    grid_device:refresh()
    tpage = page
end

-- redraw toolbar at bottom row of grid
function grid_redraw_ctrl()
    grid_device:led(1, 8, pause == 1 and maxgrid or inact) -- pause
    for button = 3, 6 do
        grid_device:led(button, 8, mute[button - 2] == 1 and maxgrid or inact) -- mutes(1-4)
    end
    grid_device:led(8, 8, lock == 1 and maxgrid or inact) -- lock all
    grid_device:led(9, 8, inact) -- randomize all
    for button = 11, 14 do
        -- select track pages (1-4)
        grid_device:led(button, 8, (page == (button - 10)) and maxgrid or inact)
    end
    grid_device:led(16, 8, page == 0 and maxgrid or inact) -- select home page
end

-- redraw home page of grid
function grid_redraw_home()
    grid_device:led(1, 2, inact)
    grid_device:led(1, 3, inact) -- seqlen 1
    grid_device:led(2, 2, inact)
    grid_device:led(2, 3, inact) -- seqlen 2
    grid_device:led(3, 2, inact)
    grid_device:led(3, 3, inact) -- seqlen 3
    grid_device:led(4, 2, inact)
    grid_device:led(4, 3, inact) -- seqlen 4
    grid_device:led(6, 2, inact)
    grid_device:led(6, 3, inact) -- bpm coarse
    grid_device:led(7, 2, inact)
    grid_device:led(7, 3, inact) -- bpm fi
    grid_device:led(10, 2, inact)
    grid_device:led(10, 3, inact) -- tonic
    grid_device:led(11, 2, inact)
    grid_device:led(11, 3, inact) -- scale
    grid_device:led(13, 2, inact)
    grid_device:led(13, 3, inact) -- tempo mod 1
    grid_device:led(14, 2, inact)
    grid_device:led(14, 3, inact) -- tempo mod 2
    grid_device:led(15, 2, inact)
    grid_device:led(15, 3, inact) -- tempo mod 3
    grid_device:led(16, 2, inact)
    grid_device:led(16, 3, inact) -- tempo mod 4
    grid_device:led(1, 5, inact)
    grid_device:led(1, 6, inact) -- dispersion 1
    grid_device:led(2, 5, inact)
    grid_device:led(2, 6, inact) -- dispersion 2
    grid_device:led(3, 5, inact)
    grid_device:led(3, 6, inact) -- dispersiom 3
    grid_device:led(4, 5, inact)
    grid_device:led(4, 6, inact) -- dispersion 4
    grid_device:led(13, 5, inact)
    grid_device:led(13, 6, inact) -- unassigned
    grid_device:led(14, 5, inact)
    grid_device:led(14, 6, inact) -- unassigned
    grid_device:led(15, 5, inact)
    grid_device:led(15, 6, inact) -- unassigned
    grid_device:led(16, 5, inact)
    grid_device:led(16, 6, inact) -- unassigned
end

-- redraw the track view for the selected track
function grid_redraw_page()
    grid_redraw_track()

    -- draw randomness selector and rest frequency selector on row 4
    for led = 1, 7 do
        grid_device:led(led, 4, led == change[page] and maxgrid or inact)
        grid_device:led(led + 9, 4, led == restfreq[page] and maxgrid or inact)
    end

    -- draw various buttons on rows 6 and 7
    grid_device:led(1, 6, (press == 106) and maxgrid or inact) -- copy
    grid_device:led(2, 6, (press == 206) and maxgrid or inact) -- paste
    grid_device:led(4, 6, (press == 406) and maxgrid or inact) -- shift ->
    grid_device:led(5, 6, (press == 506) and maxgrid or inact) -- shift <-
    grid_device:led(12, 6, (press == 1206) and maxgrid or inact) -- transpose up
    grid_device:led(13, 6, (press == 1306) and maxgrid or inact) -- transpose down
    grid_device:led(15, 6, (press == 1506) and maxgrid or inact) -- invert
    grid_device:led(16, 6, (press == 1606) and maxgrid or inact) -- reverse
    grid_device:led(8, 7, (press == 807) and maxgrid or inact) -- track lock
    grid_device:led(9, 7, (press == 907) and maxgrid or inact) -- track clear
end

-- redraw just the sequence for the current page
function grid_redraw_track()
    -- turn off all leds on the top 2 rows
    for led = 1, seqlen[page] do
        grid_device:led(led, 1, 0)
        grid_device:led(led, 2, 0)
    end

    -- draw top 2 rows (sequence position and scale degrees)
    for led = 1, seqlen[page] do
        grid_device:led(led, 1, led == position[page] and maxgrid or inact)
        if rests[page][led] == 0 and steps[page][led] > 0 then
            local val = math.floor((steps[page][led] / #scale) * maxgrid) + 1
            if val > maxgrid then
                val = maxgrid
            end
            if val < 0 then
                val = 1
            end
            grid_device:led(led, 2, val)
        else
            grid_device:led(led, 2, 0)
        end
    end
end

-- grid events
function grid_device.key(x, y, z)
    local coord = x * 100 + y -- integer code for coordinates of grid event

    -- settings page button press events ---------------------------------------------------
    if z == 1 and page == 0 then
        press = 0
        -- coarse global tempo up
        if coord == 602 then
            tempo = tempo + 10
            params:set('bpm', tempo)
            press = coord
        end

        -- coarse global tempo down
        if coord == 603 then
            tempo = tempo - 10
            if tempo < 1 then
                tempo = 10
            end
            params:set('bpm', tempo)
            press = coord
        end

        -- fine global tempo up
        if coord == 702 then
            tempo = tempo + 1
            params:set('bpm', tempo)
            press = coord
        end

        -- fine global tempo down
        if coord == 703 then
            tempo = tempo - 1
            if tempo < 1 then
                tempo = 1
            end
            params:set('bpm', tempo)
            press = coord
        end

        -- tonic up
        if coord == 1002 then
            tonicnum = tonicnum + 1
            if tonicnum > 12 then
                tonicnum = 1
            end
            center = 48 + (tonicnum - 1) -- tonic center
            scale = music.generate_scale_of_length(center - 12, music.SCALES[mode].name, 24)
            press = coord
        end

        -- tonic down
        if coord == 1003 then
            tonicnum = tonicnum - 1
            if tonicnum < 1 then
                tonicnum = 12
            end
            center = 48 + (tonicnum - 1) -- tonic center
            scale = music.generate_scale_of_length(center - 12, music.SCALES[mode].name, 24)
            press = coord
        end

        -- scale up
        if coord == 1102 then
            mode = mode + 1
            if mode > 47 then
                mode = 1
            end
            center = 48 + (tonicnum - 1) -- tonic center
            scale = music.generate_scale_of_length(center - 12, music.SCALES[mode].name, 24)
            press = coord
        end

        -- scale down
        if coord == 1103 then
            mode = mode - 1
            if mode < 1 then
                mode = 47
            end
            center = 48 + (tonicnum - 1) -- tonic center
            scale = music.generate_scale_of_length(center - 12, music.SCALES[mode].name, 24)
            press = coord
        end

        -- sequence lengths for tracks 1-4
        if x > 0 and x < 5 and (y == 2 or y == 3) then
            local track = x
            if y == 2 then
                seqlen[track] = seqlen[track] + 1
                if seqlen[track] > 16 then
                    seqlen[track] = 1
                end
            else
                seqlen[track] = seqlen[track] - 1
                if seqlen[track] < 1 then
                    seqlen[track] = 16
                end
            end
            if reverse_play[track] == 0 then
                position[track] = 0
            else
                position[track] = seqlen[track] + 1
            end
            press = coord
        end

        -- dispersion parameter for tracks 1-4
        if x > 0 and x < 5 and (y == 5 or y == 6) then
            local track = x
            if y == 5 then
                dispersion[track] = dispersion[track] + 1
                if dispersion[track] > 10 then
                    dispersion[track] = 10
                end
            else
                dispersion[track] = dispersion[track] - 1
                if dispersion[track] < 0 then
                    dispersion[track] = 0
                end
            end
            press = coord
        end

        -- tempo modifier for tracks 1-4
        if x > 12 and (y == 2 or y == 3) then
            local x_offset = x - 12
            if y == 2 then
                tempomod[x_offset] = tempomod[x_offset] + 1
                if tempomod[x_offset] > 8 then
                    tempomod[x_offset] = 8
                end
            else
                tempomod[x_offset] = tempomod[x_offset] - 1
                if tempomod[x_offset] < 1 then
                    tempomod[x_offset] = 1
                end
            end
            press = coord
        end

        -- re-sync all sequences
        if x > 12 and (y == 5 or y == 6) then
            sync_tracks()
            press = coord
        end
    end

    -- track page button press events ---------------------------------------------------
    if z == 1 and page > 0 then

        -- change probability (row 4, left side)
        if y == 4 and x < 8 then
            change[page] = x
        end

        -- rest frequency (row 4, right side)
        if y == 4 and x > 9 then
            restfreq[page] = x - 9
        end

        -- sequence position (top row)
        if y == 1 then
            position[page] = x
        end

        -- toggle rest (2nd row from top)
        if y == 2 then
            rests[page][x] = 1 - rests[page][x]
        end

        -- copy sequence (row 6, col 1)
        if y == 6 and x == 1 then
            for step = 1, 16 do
                steps_copy[step] = steps[page][step]
                rests_copy[step] = rests[page][step]
            end
            pagecopy = page
            press = coord
        end

        -- paste sequence (row 6, col 2)
        if y == 6 and x == 2 then
            for step = 1, 16 do
                steps[page][step] = steps_copy[step]
                rests[page][step] = rests_copy[step]
            end
            seqlen[page] = seqlen[pagecopy]
            change[page] = 1
            press = coord
        end

        -- shift left (row 6, col 4)
        if coord == 406 then
            shift_left()
            press = coord
        end

        -- shift right (row 6, col 5)
        if coord == 506 then
            shift_right()
            press = coord
        end


        -- scalar transpose down (row 6, col 12)
        if coord == 1206 then
            for step = 1, seqlen[page] do
                steps[page][step] = steps[page][step] - 1
            end
            press = coord
        end

        -- scalar transpose up (row 6 col 13)
        if coord == 1306 then
            for step = 1, seqlen[page] do
                steps[page][step] = steps[page][step] + 1
            end
            press = coord
        end

        -- invert (row 6 col 15)
        if coord == 1506 then
            for step = 1, seqlen[page] do
                steps[page][step] = (12 - steps[page][step]) + 12
            end
            press = coord
        end

        -- forward/reverse/ping-pong (row 6 col 16)
        if coord == 1606 then
            play_mode[page] = play_mode[page] + 1
            if play_mode[page] > 2 then
                play_mode[page] = 0  -- mode "wraps" rather than preserving previous
                pingpong[page] = false
            elseif play_mode[page] == 2 then
                pingpong[page] = true
                reverse_play[page] = false  -- we can only get here if we were reversed
            end
            if not pingpong[page] then  -- play_mode[page] *cannot* be 2
                reverse_play[page] = not reverse_play[page]
            end
            press = coord
        end

        -- lock track (row 7 col 8  -- sets randomness for track to 0)
        if coord == 807 then
            change[page] = 1
            press = coord
        end

        --  clear track (row 7 col 9)
        if coord == 907 then
            change[page] = 1
            restfreq[page] = 1
            for step = 1, 16 do
                steps[page][step] = 15
                rests[page][step] = 1
            end
            press = coord
        end
    end

    -- toolbar button press events ---------------------------------------------------
    if z == 1 and y == 8 then

        -- pause all sequences (row 8, col 1)
        if coord == 108 then
            pause = 1 - pause
            if pause == 0 then
                clk:start()
            else
                clk:stop()
            end

            -- clear all note ons
            if pause == 1 then
                for track = 1, 4 do
                  trackout = 'output' .. track
                    if mnote[track] > 0 then
                        if params:get(trackout) == 2 or params:get(trackout) == 3 then
                            engine.noteKillAll()
                        end
                        if (params:get(trackout) == 1 or params:get(trackout) == 3) then
                            midi_device:note_off(mnote[track], 0, track)
                        end
                    end
                end
            end
        end

        -- mute tracks (row 8 cols 3-6)
        if y == 8 and (x >= 3 and x <= 6) then
            mute[x - 2] = 1 - mute[x - 2]
        end

        -- lock all tracks (row 8 col 8)
        if y == 8 and x == 8 then
            lock = 1 - lock
            for track = 1, 4 do
                change[track] = 1
            end
            grid_device:led(x, y, maxgrid)
            grid_device:refresh()
        end

        -- clear all tracks (row 8 col 9)
        if y == 8 and x == 9 then
            for track = 1, 4 do
                change[track] = 1
                restfreq[track] = 1
                for step = 1, seqlen[track] do
                    steps[track][step] = 15
                    rests[track][step] = 1
                end
            end
            press = coord
        end

        -- select track page (row 8 cols 11-14)
        if y == 8 and (x >= 11 and x <= 14) then
            page = x - 10
        end

        -- select settings page (row 8 col 16)
        if y == 8 and x == 16 then
            page = 0
        end

        -- light up a pressed button
        if press > 0 then
            grid_device:led(x, y, maxgrid)
            grid_device:refresh()
        end
    end

    -- button unpressed events
    if z == 0 then
        if press > 0 then
            grid_device:led(x, y, inact)
            press = 0
        else
            grid_device:led(x, y, 0)
            grid_device:refresh()
        end
    end

    -- pause led
    if pause == 1 then
        grid_device:led(1, 8, maxgrid)
    else
        grid_device:led(1, 8, inact)
    end

    -- mute leds
    for track = 1, 4 do
        if mute[track] == 1 then
            grid_device:led(2 + track, 8, maxgrid)
        else
            grid_device:led(2 + track, 8, inact)
        end
    end

    -- track select leds
    for track = 1, 4 do
        if page == track then
            grid_device:led(10 + track, 8, maxgrid)
        else
            grid_device:led(10 + track, 8, inact)
        end
    end

    -- settings page led
    if page == 0 then
        grid_device:led(16, 8, maxgrid)
    else
        grid_device:led(16, 8, inact)
    end

    -- turn off lock led if any track is unlocked
    for track = 1, 4 do
        if change[track] > 1 then
            lock = 0
        end
    end
    if lock == 1 then
        grid_device:led(8, 8, maxgrid)
    else
        grid_device:led(8, 8, inact)
    end

    -- redraw
    redraw()
    grid_redraw()
end

function count()
    tick = tick + 1

    -- moves the sequence ahead by one step and turns on/off notes
    for track = 1, 4 do
        trackout = 'output' .. track

        -- advance the sequence position, depending on the tempo modifier
        if tick % tempomod[track] == 0 then
            if not reverse_play[track] then
                position[track] = (position[track] % seqlen[track]) + 1
                if pingpong[track] and position[track] == seqlen[track] then
                    reverse_play[track] = not reverse_play[track]  -- flip it at the end
                end
            else
                -- fix up reset for reverse play
                if position[track] == 0 then
                    position[track] = seqlen[track] + 1  -- wrap position to the end
                end
                -- Thanks, S.O.! https://stackoverflow.com/a/39740009
                position[track] = ((position[track] - 1) + 1 * seqlen[track] - 1)
                                  % seqlen[track] + 1
                if pingpong[track] and position[track] == 1 then
                    reverse_play[track] = not reverse_play[track]
                end
            end

            -- update the sequence
            update_sequence(track)

            -- turn off the last note
            if mnote[track] > 0 or mute[track] == 1 then
                if params:get(trackout) == 2 or params:get(trackout) == 3 then
                    engine.noteOff(mnote[track])
                end
                if (params:get(trackout) == 1 or params:get(trackout) == 3) then
                    midi_device:note_off(mnote[track], 0, track)
                end
            end

            local stepvalue = steps[track][position[track]]
            local adjstepvalue
            adjstepvalue = stepvalue
            if stepvalue > #scale then
              adjstepvalue = #scale
            end
            if stepvalue < 1 then
              adjstepvalue = 1
            end
            local note = scale[adjstepvalue]

            -- turn on a note unless there is a rest
            if rests[track][position[track]] == 0 and note ~= nil then
                note = note + transpose
                if note > 0 and mute[track] == 0 then
                    if params:get(trackout) == 2 or params:get(trackout) == 3 then
                        local freq = music.note_num_to_freq(note)
                        engine.noteOn(note, freq, 90)
                    end
                    if (params:get(trackout) == 1 or params:get(trackout) == 3) then
                        midi_device:note_on(note, 90, track)
                    end
                    if params:get(trackout) == 4 then
                      crow.ii.jf.play_voice(track, (note - 60) / 12, 5)
                    end
                    if params:get(trackout) == 5 then
                      crow.output[1].volts = (note - 60) / 12
                      crow.output[2].execute()
                    end
                    if params:get(trackout) == 6 then
                      crow.output[3].volts = (note - 60) / 12
                      crow.output[4].execute()
                    end
                    mnote[track] = note
                end
            end
        end
    end
    grid_redraw()
end

function update_sequence(track)
    -- updates each sequence in a probabilistic manner
    -- the dispersion parameter controls how big of a jump the sequence can make
    local chg = changelist[change[track]]
    local rfq = rflist[restfreq[track]]
    if (math.random() < chg) then
        local tposition = position[track] - 1
        if tposition < 1 then
            tposition = seqlen[track]
        end
        local delta = round(box_muller() * (dispersion[track] / 5))
        delta = delta + round((15 - steps[track][position[track]]) * .05)
        steps[track][position[track]] = steps[track][tposition] + delta
        if steps[track][position[track]] > #scale then
            steps[track][position[track]] =
                #scale - (steps[track][position[track]] - #scale)
        end
        if steps[track][position[track]] < 1 then
            steps[track][position[track]] = 1 - (steps[track][position[track]])
        end
        if (math.random() < rfq) then
            rests[track][position[track]] = 1
        else
            rests[track][position[track]] = 0
        end
    end
end

function key(n, z)
    -- while held, button 3 displays the midi notes of the sequence on the selected track
    if n == 3 and z == 1 then
        if not seqlen[page] then -- we're on the settings page!
            return
        end
        screen.clear()
        local bb = ' '
        for step = 1, seqlen[page] do
            local aa = scale[steps[page][step]]
            if rests[page][step] == 1 then
                aa = 0
            end
            if aa < 100 then
                if aa == 0 then
                    aa = ('  ' .. aa)
                else
                    aa = (' ' .. aa)
                end
            end
            bb = (bb .. aa .. ' ')
        end
        screen.move(0, 10)
        screen.text('Track #' .. page)
        for track = 1, 4 do
            screen.move(0, 20 + 10 * track)
            local cc = string.sub(bb, (track - 1) * 16 + 1, (track - 1) * 16 + 16)
            screen.text(cc)
        end
        screen.update()
    end
    if n == 3 and z == 0 then
        redraw()
    end
end

function enc(n, delta)
    if n == 2 then  -- change seq length, with wrap
        if delta > 0 then
            seqlen[page] = seqlen[page] + 1
            if seqlen[page] > 16 then
                seqlen[page] = 1
            end
        elseif delta < 0 then
            seqlen[page] = seqlen[page] - 1
            if seqlen[page] < 1 then
                seqlen[page] = 16
            end
        end
        redraw()
        tpage = -99  -- hack
        grid_redraw()
    elseif n == 3 then  -- shift sequence L/R
        if pause == 0 then  -- doesn't seem to work well unless we're playing
            if delta > 0 then
                shift_right()
            elseif delta < 0 then
                shift_left()
            end
        end
    end
end

function shift_left()
    -- shifts the sequence to the left, wrapping the first note to the end of the sequence
    -- rewrite this using deepcopy
    local stp = steps[page][1]
    local rst = rests[page][1]
    for step = 1, (seqlen[page] - 1) do
        steps[page][step] = steps[page][step + 1]
        rests[page][step] = rests[page][step + 1]
    end
    steps[page][seqlen[page]] = stp
    rests[page][seqlen[page]] = rst
end

function shift_right()
    -- shifts the sequence to the right, wrapping the last note to the start of the sequence
    -- rewrite this using deepcopy
    local stp = steps[page][seqlen[page]]
    local rst = rests[page][seqlen[page]]
    for step = seqlen[page], 2, -1 do
        steps[page][step] = steps[page][step - 1]
        rests[page][step] = rests[page][step - 1]
    end
    steps[page][1] = stp
    rests[page][1] = rst
end

function deepcopy(orig)
    -- make a copy of a table instead of making a direct reference
    local orig_type = type(orig)
    local copy
    if orig_type == 'table' then
        copy = {}
        for orig_key, orig_value in next, orig, nil do
            copy[deepcopy(orig_key)] = deepcopy(orig_value)
        end
        setmetatable(copy, deepcopy(getmetatable(orig)))
    else -- number, string, boolean, etc
        copy = orig
    end
    return copy
end

function sync_tracks()
    for track = 1, 4 do
        position[track] = 0
    end
end

function clear_all_notes()
    engine.noteKillAll()
    for track = 1, 4 do
        trackout = 'output' .. track

        for note = 1, #scale do
            if (params:get(trackout) == 1 or params:get(trackout) == 3) then
                midi_device:note_off(scale[note], 0, track)
            end
        end
    end
end

-- box_muller simulates normally distributed random numbers from uniform random numbers
function box_muller()
    return math.sqrt(-2 * math.log(math.random())) * math.cos(2 * math.pi * math.random())
end

-- round to nearest integer
function round(num)
    local under = math.floor(num)
    local upper = math.floor(num) + 1
    local underV = -(under - num)
    local upperV = upper - num
    if (upperV > underV) then
        return under
    else
        return upper
    end
end

-- gratuitous opening animation
function opening_animation()
    for a = 8, 1, -1 do
        grid_device:all(0)
        for i = 1, 8 do
            for j = 1 + (a - 1), 16 - (a - 1) do
                grid_device:led(j, i, math.random(0, 15))
            end
        end
        grid_device:refresh()
        sleep(0.1)
    end
    for a = 1, 8 do
        grid_device:all(0)
        for i = 1, 8 do
            for j = 1 + (a - 1), 16 - (a - 1) do
                grid_device:led(j, i, math.random(0, 15))
            end
        end
        grid_device:refresh()
        sleep(0.1)
    end
    grid_device:all(0)
    grid_device:refresh()
end

-- pause lua code
function sleep(secs)
    local ntime = os.clock() + secs
    repeat
    until os.clock() > ntime
end

function cleanup ()
  clk:stop()
end