Remove silence from start of midi file

[zero-nnkn]

I'm working with midi files that have pretty long first silences, and I want to get rid of them. I think this is quite a necessary requirement, but I can't find the pre-written tools to support it. That's why I wanted to write a function to do this. The simple idea is to subtract the start time of all the notes of all tracks by an interval equal to the start time of the first note (the earliest).

Here is the source code to implement that idea. I would like to ask if something is wrong with my method or my understanding of how to use muspy.Music.

import muspy as mp


min = mp.read_midi('midi-file-path.mid', backend='mido')

def trim_silence(music: mp.Music):
    music = music.deepcopy()
    # Collect notes
    notes = []
    for track in music.tracks:
        notes.extend(track.notes)

    # Raise an error if no notes is found
    if not notes:
        raise RuntimeError("No notes found.")
    
    # Sort the notes
    notes.sort(key=lambda n: n.time)
    start_time = notes[0].time

    # Ship the start time to zero
    for it in range(len(music.tracks)):
        for inote in range(len(music.tracks[it].notes)):
            music.tracks[it].notes[inote].time -= start_time
    
    return music