For most students, it makes more sense to pay for services like Spotify or Rdio rather than shell out for dozens of individual songs each month. But even the $9.99 monthly rate both companies normally charge can prove a bit much for undergrads. So Rdio is trying to sweeten the deal by cutting that fee in half; current college students can now sign up for an Rdio Unlimited account for just $4.99 per month. The offer, announced earlier this month, is valid in the US only and requires a valid .edu email address to redeem. There are other requirements, too. The $4.99 promotion is good for a maximum of four years (which makes sense if you're starting as a freshman), and a social security number is also required during the automated signup process if you want to save the $5.00.