def note_value_to_string(list_of_dict_keys_time):
    """
    Convert note arrays (e.g. array([36, 48, 60]) to strings (e.g. '36,48,60')

    Arguments:
    ==========
    - list_of_dict_keys_time : list
        List of dict of timesteps and note played
        A list with len of batch_song (16), each element is a dict
        Each dict has keys (timestep numbers: 30,31,35,...) vs.
        values (note arrays, e.g. array([36, 48, 60])


    Returns
    =======
    - list_of_dict_time_notestr: list
        List of dict of timesteps and note played
        A list with len of batch_song (16), each element is a dict
        Each dict has keys (timestep numbers: 30,31,35,...) vs.
        values (note strings, e.g. '36,48,60')
    """
    list_of_dict_time_notestr = []
    for song_dict in list_of_dict_keys_time:
        dict_time_notestr = {}
        for time in song_dict:
            note_str = ','.join(str(a) for a in song_dict[time])
            dict_time_notestr[time] = note_str
        list_of_dict_time_notestr.append(dict_time_notestr)
    return list_of_dict_time_notestr