Hello, I am a music teacher. I have been emailing my students an email with a piano and vocal recording (on the same mp3). Most of the time, the way it works is that they download the email into Garage Band file Transfer, put the mp3 into GB, and then they have the karaoke track they're supposed to sing along to. Today, I had a student who said that when he listened to the file in his email, it sounded right, but then when he put it in GB, it played only the piano part of the recording. How is this even possible?