u want my idea?!!!
look , u can pay mp3 player from market , u will find it very cheap nowadays
remove the plastic cover and interface it with the micro-controller u want
u will find it very easy and can put many things to play
But you don't have the FEELING when you did the whole thing by yourself
beginning with the prototype.
That's what a electronic enthusiast, like me, would say.
However I used a cheap timer switch for my sunset/dawn project for my geckos,
it's quite the path mr_byte31 suggested