Billy Joel says there was once "bad blood" between him and Elton John. In the second part of a new two-part HBO documentary Billy Joel: And So It Goes, the "Piano Man" singer opens up about how the "Your Song" musician's public declaration that he needed rehab caused tension between them.

And So It Goes,” the singer is opening up about some tough moments with longtime friend and tourmate Elton John.

Billy Joel acknowledged “bad blood” between himself and Elton John in the second installment of his two-part HBO documentary “Billy Joel: And So It Goes,” released Friday. Joel explained the pair’s fallout occurred after John publicly insisted he needed to go to rehab.