Boris shared a link to this article Embedded MP3 module:
This embedded MP3 module is an universal and compact circuit (37 mm x 27 mm) for playing MP3 audio files. The MP3 module can be used in embedded systems.
The MP3 files (up 65,536) are stored in a micro SDcard.
Controlling the module could be done either by buttons and digital inputs or via TTL serial interfaces.
The MP3 module (developed by Luca Pascarella info at lpsystems dot eu) is based on MP3 converter VS1011 and a PIC24 and can play up to 65,536 songs or voice messages stored in a microSD.