First Go for the this http://developer.android.com/guide/topics/media/mediaplayer.html
Read the documentation , discover a little about the Media Player class that is what are its Fields , is it a subclass and finally the Interface
Then here are some links :
www.youtube.com/watch?v=-zGS_zrL0rY
http://www.verious.com/board/58211/building-a-custom-android-audio-player/
http://www.youtube.com/watch?v=irdwVCDcMug
http://www.tutorialspoint.com/android/android_mediaplayer.htm