Whose version of unchained melody was played on Quantum Leap?

The version of "Unchained Melody" that was played on the television series *Quantum Leap* was by The Righteous Brothers.

It became a recurring theme song for the show, playing during Sam Beckett's leaps and often during poignant or emotional moments. The song was so iconic for the show that it became synonymous with *Quantum Leap* itself.