import mido


def process(midi: mido.MidiFile, tracks: set[int] | None = None) -> mido.MidiFile:
    cleaned_midi = mido.MidiFile()
    cleaned_midi.ticks_per_beat = midi.ticks_per_beat

    for i, track in enumerate(midi.tracks):
        if tracks is not None and i not in tracks:
            cleaned_midi.tracks.append(track)
            continue

        cleaned_track = mido.MidiTrack()
        last_state = {}
        last_msg = None

        for msg in track:

            if last_msg is not None and msg == last_msg:
                continue

            if msg.type in ['control_change', 'program_change', 'pitchwheel', 'aftertouch', 'channel_pressure']:
                channel = msg.channel
                key = f"{msg.type}_{channel}"
                if key in last_state and last_state[key] == msg:
                    continue
                last_state[key] = msg
                cleaned_track.append(msg)
            elif msg.type == 'note_off':
                cleaned_track.append(msg)
            elif msg.type == 'note_on' and msg.velocity == 0:
                cleaned_track.append(msg)
            else:
                cleaned_track.append(msg)

            last_msg = msg

        cleaned_midi.tracks.append(cleaned_track)

    return cleaned_midi