This might be a little time consuming but it totally works:
Sign out of Amazon. Go to http://www.guerrillamail.com/
. That website has disposable email addresses to stop spam and what not. It gives you an address. Copy the address. Find an album or mp3 you want. Click on the "redeem a gift card promotion" button under "give song as a gift". Put in the momrocks promo code. Then create a new account with that disposable email address. You can put anything for the info aka it doesn't have to be valid. Once you use up your 2 mp3 credits, log out. Go back to guerrilla mail and refresh the page. It'll give you another email address. Do it again. I just went through about 20 email addresses and got 2 albums out of that. If anyone has any questions, just quote me and ask.