Non-fretted (non-guitar) instruments transposing for standard notation

[mxAlexG]

Hello,
Judging by what I understood from issue#139 and the behavior I am getting, alphaTab renders non-guitar tracks in standard notation an octave lower than they are in the rendered tablature bars because guitars (including bass guitar) are written one octave higher than sounding pitch. An example would be like the following:

NON-GUITAR INSTRUMENTS:
Tablature: G5 (G String - 12th fret) --> Standard Notation: G4 --> displayValue(midi note): G4 (67)

GUITAR INSTRUMENTS:
Tablature: G5 (G String - 12th fret) --> Standard Notation: G5 --> displayValue(midi note): G5 (79)

Is this correct?

My guess is that alphaTabs performs this octave lower transposing step based on the midi program numbers? or some value that is relevant to GuitarPro file format spec?

What is the best way to tell which track will be identified as a guitar instrument that will get this octave lower transposing step?

Thanks.

[Danielku15]

Guitar Pro 6-8 files have this transposition encoded inside the data model. So it is Guitar Pro who decides there which tracks are visually transposed. In alphaTab this is handled as Staff.displayTranspositionPitch

alphaTab/src/importer/GpifParser.ts

Lines 1045 to 1075 in f8da16b

	private parsePartSounding(track: Track, node: XmlNode): void {
	for (let c of node.childNodes) {
	if (c.nodeType === XmlNodeType.Element) {
	switch (c.localName) {
	case 'TranspositionPitch':
	for (let staff of track.staves) {
	staff.displayTranspositionPitch = parseInt(c.innerText);
	}
	break;
	}
	}
	}
	}
	private parseTranspose(track: Track, node: XmlNode): void {
	let octave: number = 0;
	let chromatic: number = 0;
	for (let c of node.childNodes) {
	if (c.nodeType === XmlNodeType.Element) {
	switch (c.localName) {
	case 'Chromatic':
	chromatic = parseInt(c.innerText);
	break;
	case 'Octave':
	octave = parseInt(c.innerText);
	break;
	}
	}
	}
	for (let staff of track.staves) {
	staff.displayTranspositionPitch = octave * 12 + chromatic;

In alphaTex with explicit tunings the transposition is disabled for 3 specific tunings (see also):

alphaTab/src/importer/AlphaTexImporter.ts

Lines 718 to 721 in f8da16b

	if (text === 'piano' || text === 'none' || text === 'voice') {
	// clear tuning
	this._currentStaff.stringTuning.tunings = [];
	this._currentStaff.displayTranspositionPitch = 0;

In alphaTex for automatic tunings it is aligned a bit more with Guitar Pro (I analyzed there once all instrument types manually in GP):

alphaTab/src/importer/AlphaTexImporter.ts

Lines 1003 to 1041 in f8da16b

	if (program == 15 || program >= 24 && program <= 31) {
	// dulcimer+guitar E4 B3 G3 D3 A2 E2
	this._currentStaff.displayTranspositionPitch = -12;
	this._currentStaff.stringTuning.tunings = Tuning.getDefaultTuningFor(6)!.tunings;
	} else if (program >= 32 && program <= 39) {
	// bass G2 D2 A1 E1
	this._currentStaff.displayTranspositionPitch = -12;
	this._currentStaff.stringTuning.tunings = [43, 38, 33, 28];
	} else if (program == 40 || program == 44 || program == 45 || program == 48 || program == 49 || program == 50 || program == 51) {
	// violin E3 A3 D3 G2
	this._currentStaff.stringTuning.tunings = [52, 57, 50, 43];
	} else if (program == 41) {
	// viola A3 D3 G2 C2
	this._currentStaff.stringTuning.tunings = [57, 50, 43, 36];
	} else if (program == 42) {
	// cello A2 D2 G1 C1
	this._currentStaff.stringTuning.tunings = [45, 38, 31, 24];
	} else if (program == 43) {
	// contrabass
	// G2 D2 A1 E1
	this._currentStaff.displayTranspositionPitch = -12;
	this._currentStaff.stringTuning.tunings = [43, 38, 33, 28];
	} else if (program == 105) {
	// banjo
	// D3 B2 G2 D2 G3
	this._currentStaff.stringTuning.tunings = [50, 47, 43, 38, 55];
	} else if (program == 106) {
	// shamisen
	// A3 E3 A2
	this._currentStaff.stringTuning.tunings = [57, 52, 45];
	} else if (program == 107) {
	// koto
	// E3 A2 D2 G1
	this._currentStaff.stringTuning.tunings = [52, 45, 38, 31];
	} else if (program == 110) {
	// Fiddle
	// E4 A3 D3 G2
	this._currentStaff.stringTuning.tunings = [64, 57, 50, 43];
	}

For Guitar Pro 3-5 the logic is that the display is transposed for all Midi Guitar tracks only:

alphaTab/src/importer/Gp3To5Importer.ts

Lines 377 to 378 in f8da16b

	if (GeneralMidi.isGuitar(info.program)) {
	mainStaff.displayTranspositionPitch = -12;

So it is not 100% consistent across all file format and would maybe need some alignment. But that's how it is done currently.

https://music.stackexchange.com/questions/101432/why-is-guitar-music-written-one-octave-higher
https://hubguitar.com/sight-reading/octaves-and-transposition

[mxAlexG]

Hi,
Thanks for the thorough answer. I appreciate it.