If you have an Amazon Student account, check your email inbox. You may have an email with the subject line: Amazon Student: $2 MP3 Credit. There is a unique code in there to add to your Amazon account and bag a free $2 MP3 credit. You have until 4/22 to use this credit or it will expire.
If you are not an Amazon student, you can become one for FREE with an .edu email account in your name. You will also get six free months of Amazon Prime Membership. Also, renewing this Amazon Prime Membership will only cost you $39 per year instead of the regular $79.