Muddy Waters, Buddy Guy, Willie Dixon – “Wee Wee Baby” (available – ha ha – on an LP that was variously referred to as Blues From Big Bill’s Copa Cabana or Folk Festival Of The Blues, and briefly on CD as Live Action. Good luck!), 3:51
This record really has to be reissued soon; it’s a document of Muddy, Howlin’ Wolf, and Buddy Guy playing live in a Chicago club in 1963 (with a couple of studio tracks from Sonny Boy Williamson and Buddy padding out the playing time), and it’s essential listening. A couple of verses after what might be Buddy Guy’s best solo on record, he hits a high, sustained D note behind Muddy’s vocal, and bassist Jack Meyers responds with a high D of his own a few beats later, making for a surreal moment of sympathetic resonance (as if the whole fragile structure of the multiverse is tuned to D). It’s a beautiful moment that could only happen because the musicians were listening to each other HARD, and playing reactively.
EDIT: Just found it on YouTube. The moment occurs about 3:50 into the video.