Custom MP3 player

The application needed is a customizable MP3 player with the ability to scan a directory and add new songs to a playlist (preferably prioritize them? well).? I addition it will need to be able to insert what is normally called a comercial spot,? simply a mp3 played from a second directory/playlist in rotating or random fashsion at predetermind intervals. This is not a commercial application. Seems like something like this should exist somewhere however if it does i have been completly unsuccessfull at locating it.