Paul McCartney - we can work it out live unplugged the official bootleg, 1991

"Unlike other artists who appeared on the show with acoustic instruments plugged into amplifiers, McCartney's instruments were entirely unplugged. Microphones were carefully placed close to guitars, pianos, etc. to pick up the sound (this can be seen on the album cover, where a large rectangular microphone is pictured in front of McCartney's acoustic guitar)."