Paul Butterfield is one of the best blues harpists, as well as one of the most successful blues musicians. The 1965 debut album 'The Paul Butterfield Blues Band' reached #123 on the Billboard charts, and is listed as number #468 on Rolling Stones 'Top 500 Albums of All Time' list.
The band features Mike Bloomfield and Elvin Bishop on guitar, Mark Naftalin on organ, Jerome Arnold on bass, and Sam Lay on drums. It's one of the first pure blues albums by a white singer, in the Chicago blues style.
This is one of the slower tunes on the album called 'Last Night':