Trying to play some mp3 files using audiomixer in CircuitPython.

mp3-beats.py

# audiomixer_demo.py -- show how to fade up and down playing loops
import time, board, audiocore, audiomixer, adafruit_mpr121, digitalio
from audiomp3 import MP3Decoder

# import PWMAudioOut & name it AudioOut
from audiopwmio import PWMAudioOut as AudioOut

# set up I2C
i2c = board.STEMMA_I2C()

# set up touchpads
touch_pad = adafruit_mpr121.MPR121(i2c)

audio = AudioOut(board.GP14)

beats = ["amenfull_22k_s16.mp3",
        "amen6_22k_s16.mp3",
        "amen7_22k_s16.mp3",
        "ohohoh2.mp3",
        "bass_hit_c.mp3",
        "bd_tek.mp3",
        "bd_zome.mp3",
        "drum_cowbell.mp3"]
#         "duck-scratch.mp3",
#         "yo.mp3",
#         "watch-this.mp3",
#         "freakie-freak.mp3"]

path = "mp3-beats/"

num_voices = len(beats)

mp3 = open(path + beats[0], "rb")
decoder = MP3Decoder(mp3)

mixer = audiomixer.Mixer(voice_count=num_voices, sample_rate=22050, channel_count=1,
                         bits_per_sample=16, samples_signed=True)
# attach mixer to audio playback
audio.play(mixer)

for i in range(len(beats)):
    decoder.file = open(path + beats[i], "rb")
    audio.play(decoder)
    print(f"file = {beats[i]}")
    mixer.voice[i].play(decoder, loop=True )
    mixer.voice[i].level = 0.0
time.sleep(1.0)  # let last play a bit, just to make sure it plays

while True:
    for i in range(len(beats)):
        if touch_pad[i].value:
            print(f"You touched pad # {i}!")
            mixer.voice[i].level = 1.0
        else:
            mixer.voice[i].level = 0.0