Install USB sound card driver

install MP3 software:

opkg update
opkg install madplay
cd /mnt/sda1
wget --no-check-certificate  https://www.dropbox.com/s/zzowqtew6cmspsf/track39.mp3
madplay /mnt/sda1/track39.mp3
MPEG Audio Decoder 0.15.2 (beta) - Copyright (C) 2000-2004 Robert Leslie et al.
          Title: Track 39
           Year: 1999
          Genre: Pop
        Comment: , AG# F7355561
1281 frames decoded (0:00:33.4), -5.8 dB peak amplitude, 0 clipped samples
root@Arduino:/mnt/sda1# madplay /mnt/sda1/track39.mp3
MPEG Audio Decoder 0.15.2 (beta) - Copyright (C) 2000-2004 Robert Leslie et al.
          Title: Track 39
           Year: 1999
          Genre: Pop
        Comment: , AG# F7355561
1281 frames decoded (0:00:33.4), -5.8 dB peak amplitude, 0 clipped samples