Concatenating MIDI files

[frallebini]

Given two (type 1) MIDI files

mid1 = MidiFile('first.mid')
mid2 = MidiFile('second.mid')

how could I go about creating a

concat_mid = MidiFile()

such that concat_mid "plays" mid1's tracks first, and then, when mid1 is over, it starts playing mid2's tracks?

[frallebini]

I think I found a solution. I'll share it here for future reference:

mid1 = MidiFile('first.mid')
mid2 = MidiFile('second.mid')

# compute mid1 total time
time1 = 0
for track in mid1.tracks:
    for message in track:
        if message.type == 'note_on':
            time1 += message.time

# shift mid2 by time1
for track in mid2.tracks:
    for message in track:
        if message.type == 'program_change':
            message.time += time1

# merge mid1 and shifted mid2
concat_mid = MidiFile()
concat_mid.tracks = mid1.tracks + mid2.tracks
concat_mid.save('concat.mid')

[rdoursenaud]

This would have been better suited for our Discussions area.
Note that your solution is only valid for two files using the same resolution.

[frallebini]

Sorry, didn’t realize there was such a thing.

What do you mean by “resolution”?

[rdoursenaud]

Every Standard Midi File (SMF) has a "ticks per quarter note" information in the header. The delta-time used by messages is defined in ticks. Hence the resolution bit.

But I've made a mistake stating it wouldn't work since mido seems to be encoding the time information in seconds so my bit is irrelevant.
Sorry for the confusion.