There are singers, and there are interpreters.
Interpreters are a rare breed of singers. Interpreters don’t need to write their own songs, although they do on occasion; they make any song they sing their own. Interpreters can choose a song that you think could never be done by anyone except the band that first wrote, performed, and made it popular, and turn it into something totally original. They make it unforgettably their own.
Joe Cocker is an interpreter.