Fast food chain Wendy’s is teaming up with digital music service Rhapsody to give away 100 million songs to customers.

Beginning this week, anybody buying a medium or large-sized combo meal at participating Wendy’s outlets will receive a unique code redeemable for any song in Rhapsody’s 4.5 million-track catalog. The promotion will run through December, and will be supported by a national advertising campaign.

Additionally, customers will have the option to enter a sweepstakes called “Combo Up to Download” for a chance to win a 50-song bundle of free songs, or a SanDisk Sansa Rhapsody portable music player.

Finally, Rhapsody is powering a Web site for the promotion that streams music from the top artist on the Rhapsody service, and has created a specially programmed Wendy’s Radio stream.