Adam Blackstone Is a Musical Multihyphenate Who Is His Own Competition

It’s 2003 and Jay-Z is planning a farewell concert at Madison Square Garden to celebrate his retirement from music.

But his bass player is unavailable. Adam Blackstone, a jack-of-all-trades who plays bass, drums, piano, organ, tuba and sousaphone — and is also a songwriter, producer, composer and everything else under the musical sun — is more than ready to step in.

Twenty years later, Blackstone, now 40, is still working closely with Jay-Z; both are Emmy…