I would just have a global variable that starts at 1, and when you press right arrow, it adds 1 to the variable and each number relates to a song. You can also relate the same variable to animation frame.
pseudo something like :
global int track = 1
On right arrow pressed, stop audio, add one to track
On left arrow pressed, stop audio, subtract one from track
If track > 13, set track to 1
If track < 1, set track to 13
songcho, set animation frame to track
If track = 1, play song 1
If track = 2, play song 2 etc