Provide easy way to disable MIDI quantization

[alexandermorgan]

In processing a string quartet, I get the same offset values for the C and Bb in measure 2, beat 3 of the first violin in the snapshot below.

I'm running into this problem in music21 3.1.0, but not in 2.1.2. The way I use music21 to determine the offset of a note is with the following logic where event has already been filtered to make sure it has a 'Note', 'Rest', or 'Chord' type:

for y in event.contextSites():
    if y[0] is part:
        return y[1]

When I make a pandas.Series of these note, rest, or chord objects with their offsets as determined by the code above as the index, these are the first few values for the first violin:

0.000000               <music21.note.Rest rest>
3.000000                  <music21.note.Note E>
4.000000                  <music21.note.Note F>
5.500000                  <music21.note.Note A>
6.000000                  <music21.note.Note C>
6.000000                 <music21.note.Note B->
6.333333               <music21.note.Rest rest>
6.500000                  <music21.note.Note A>
7.000000                 <music21.note.Note B->
7.500000                  <music21.note.Note D>

Should I be using contextSites() differently in 3.1.0, or is there something else I'm missing? Just let me know if you'd like me to send the file. Thanks.

[alexandermorgan]

In case it's important, the file I have for this piece is in midi.

[mscuthbert]

Yes, MIDI files are quantized because there are many performed MIDI files that would otherwise be a mess. Either disable quantization in the MIDI or much better preprocess MIDI in Finale or something and export to XML.

[alexandermorgan]

Ok, so this is the new expected behavior, thank you. I looked through the documentation to find where quantize() gets called but I couldn't find it. If we import a midi file and then run .recurse() on its parts, where can I pass an argument to disable quantization? I couldn't find one in the .recurse() or .parseFile() docs arguments.

score = music21.converter.parseFile('piece_pathname.midi')
recursed_parts = [part.recurse() for part in score.parts]

[mscuthbert]

I've changed the name of the issue to reflect the next work to be done. If you do a debugger through the system, I think you can see where the quantization happens and see a way to disable it, but it's not easily user exposed right now. I don't think I'll be able to get to this during this term though however.

[alexandermorgan]

@mscuthbert may I ask what the status of this issue is? Thanks.

[mscuthbert]

I still don't think I'll be able to get to this anytime soon -- I think it's best to run midi files through a better MIDI -> MusicXML converter (musescore is scriptable) and load those first.