def METHOD_NAME(tracks):
    """Returns all events from the track grouped per and mapped to time-step.
    every time step has a dictionary with the events per track at that time.
    """
    d = collections.defaultdict(dict)
    for n, track in enumerate(tracks):
        for time, evs in parser.time_events_grouped(
                parser.parse_midi_events(track)):
            d[time][n] = evs
    return d