These four famous songs feature backing vocals from legends, and you probably had no idea they were featured at all.

Behind every great hit, there's often an unexpected voice! Join us as we count down the songs where famous artists lent their vocal talents in supporting roles. From rock legends to pop icons ...

Sure, not every song will fit the bill, but there are quite a few that work really well sang a cappella. In this gallery, we list some of the best songs to sing a cappella.

The Unlikely Rise of an a Cappella Anthem Why an obscure 1990s rock song has such staying power.