some interesting things you may or may not know:
Leon Russell wrote "This Diamond Ring" for Gary Lewis and the Playboys.

Steve Stills played guitar for Judy Collins, for whom he wrote "Suite Judy Blue Eyes" and "Helplessly Hoping"; the boy had it bad (and that ain't good).

Homer and Jethro did a live album called (appropriately) "Live at the Country Club" backed up by, among others, Boots Randolph of "Yakety Sax" fame. I believe Floyd Cramer, the great Nashville pianist was also on that record. It's a very funny record and the playing is remarkable.