Keith Jarrett is well-known as an excellent jazz pianist but his second album “Restoration Ruin”, released in 1968, is a different beast entirely.
For one thing he plays guitar on all 10 tracks and piano on only two of them. And he sings.
He plays all the instruments throughout the album in fact, apart from the string quartet which appears on half of them.
He plays harmonica, recorder, soprano sax, guitar, bass guitar, bongos, tambourine, drums, piano, organ and sistra (shakers).
It’s not exactly his finest hour on record, though it’s all well-played, and he was probably wise to knock the singing on the head, but it’s an interesting artifact at least.
Any other artists you know who have gone so thoroughly off-piste?