How can I have a song played "equally" on both earphones?

What I mean is, one of my earphones doesn't work, and the other does, but for some reaon aroundhalf of the songs (the guitar playing) was played on one earphone, whereas the other half (the singing) was on the other. Seeing as one is broken, I can only hear the singing. its on an ipod touch by the way. Do any of you know how I can change it so I can listen to the entirety of a song on one earphone? thanks.