I am currently attempting to create an mp3 mellotron controlled by arduino.
I purchased 10 Coby 1GB mp3 players. They were about $8.50 each found through bizrate.com. The idea for the mellotron came from Make a mellotron out of walkmans at makezine.com when I was trying to figure out ways to create multiple audio output where I can control each output individually. Each player will have 1-2 speakers (possible amp) and the volume and track controlled through voltage sent to the mp3 through the ardiuno. I hope to have a few of them wired up and posted in the next week.