For a flat monthly fee, you can download and listen to as many songs as you want, as often as you want. The songs are yours to play for as long as your Zune Pass is valid.

You can get a Zune Pass that's good for either one or three months at a time. Charge your subscription directly to your credit card or enter a code from a prepaid card.
GET A ZUNE PASS SUBSCRIPTION
DOWNLOAD MUSIC WITH A ZUNE PASS
Note
Some songs and albums at Zune Marketplace are only available as a purchase.
Songs you get with a Zune Pass can be copied to up to three computers and three Zunes, but they can't be burned to CDs. If you want to do that, buy those songs with Microsoft Points.