How Do I Add Note to Track with a Channel Number? #592

JeffRocchio · 2024-07-27T16:17:07Z

JeffRocchio
Jul 27, 2024

I am trying to add notes to a MIDI track in a mido.MidiFile. The pre-existing track I am trying to add notes to has all it's note on channel 1 (there are two tracks in the file, track-0 is using channel-0, track-1 is using channel-1 - t 8000 he original file was exported from a score in Musescore).

The append method, with the 'note_on' message, only takes note, velocity and time. And the result of adding notes track-1 is that all my added notes then show up as having been assigned to channel-0.

So: How do I control which channel 'note_on' / 'note_off' get assigned to?

UPDATE on 7/27:

Update: I did find a workaround for this. I noticed there is a 'private' function on the mido.Message object that allows you to set a specific parameter of a message instance, so I am using that to set the channel parameter for my added notes. When I do this everything seems to now work OK in terms of my modified .mid file playing ok in MIDI players.

fwiw, below is the source from the function where I am adding my notes:

def _populateCountIn(self, song):
    """ Description: Populate CountIn track with count-in sequence as sped'd in song.countIn.countInModel[][]
    Param:  song :Song class - Song object instance
    Note-1: Note that I am here assuming we have already made a call to countIn._buildCountModel() as
            part of the song spec display and user confirm of specs phase. I don't see why this
            would ever not be true, and I prefer to use the model as seen and confirmed by the user
            rather than risk regenerating it anew here.
    Note-2: I am confused about channel usage in a MIDI file. The mido append 'note_on' message
            function does not permit a param for the note's channel number. Yet when you append
            a new note_on message to a track mido automatically adds 'channel=0' to the message.
            I can see that there is a 'private' function for the mido.Message object that
            allows you to set a specific parameter of a message instance, so I am using that
            to set the channel param for the added counting notes. When I do this the "Drumstick
            MIDI Player" for Linux and the "Midi Clef" player for Android gets the track names,
            channels, and instruments all correct. When I don't both of those apps get all
            mixed up. So channel attributes really do matter.
    """
    #-----| Giving names to the countModel 2D matrix columns
    #measure = 0 # <-- We don't use this here
    noteIdx = 1
    duration = 2
    #-----| Declare local helper variables
    ctTrackIdx = self.countTrackIdx #       <-- mido track # of the count-in track I added
    ctChannel = self.countTrackChannel #    <-- channel # I've assigned from available, open, channels
    placeNoteAtTime = self.songStartTime #  <-- MIDI clicks to play 1st note at to get a full measure of silence
    #-----| Add the count-in notes to the count in output track
    for i, row in enumerate(song.countModel):
        ctNote = song.countIn.notes[row[noteIdx]]
        ctDuration = row[duration]
        msg = mido.Message('note_on', note=ctNote, velocity=64, time=placeNoteAtTime)
        msg._setattr('channel', ctChannel) #<-- 'cheat' for setting correct channel #
        song.outputMIDI.midiOut.tracks[ctTrackIdx].append(msg)
        msg = mido.Message('note_off', note=ctNote, velocity=0, time=ctDuration)
        msg._setattr('channel', ctChannel)
        song.outputMIDI.midiOut.tracks[ctTrackIdx].append(msg)
        self.songStartTime += ctDuration
        placeNoteAtTime = 0 #               <-- We've appended 1st note, so now set this zero for all remaining```

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mido

How Do I Add Note to Track with a Channel Number? #592

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mido

How Do I Add Note to Track with a Channel Number? #592

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JeffRocchio Jul 27, 2024

UPDATE on 7/27:

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JeffRocchio
Jul 27, 2024