import mido


def process(midi: mido.MidiFile, vel_min: int, vel_max: int, tracks: set[int] | None = None) -> mido.MidiFile:
    # Collect current velocity range from note_on messages in selected tracks
    cur_min = 127
    cur_max = 0
    for i, track in enumerate(midi.tracks):
        if tracks is not None and i not in tracks:
            continue
        for msg in track:
            if msg.type == 'note_on' and msg.velocity > 0:
                if msg.velocity < cur_min:
                    cur_min = msg.velocity
                if msg.velocity > cur_max:
                    cur_max = msg.velocity

    cur_range = cur_max - cur_min if cur_max > cur_min else 1

    # Remap velocities to new range
    for i, track in enumerate(midi.tracks):
        if tracks is not None and i not in tracks:
            continue
        for msg in track:
            if msg.type == 'note_on' and msg.velocity > 0:
                ratio = (msg.velocity - cur_min) / cur_range
                msg.velocity = round(vel_min + ratio * (vel_max - vel_min))
                msg.velocity = max(1, min(127, msg.velocity))

    return midi