John Lennon, Paul McCartney, Ringo Starr and assistant Mal Evans, sitting at three different pianos, simultaneously struck an E-Major chord. (In all, it took nine takes before all four struck the chord in perfect unison.) Producer George Martin then overdubbed the same chord on a harmonium to extend the effect.
The entire chord recording (lasting 53 seconds) was then overdubbed three times (thus tripling it to NINE pianos!) and attached to the end of the song. The length of the fadeout was extended even further by gradually bringing up the volume control in the studio. (Listen closely at high volume and you'll hear rustling papers and a creaking piano stool)
Can you imagine what the playback of this must have felt like that night? (One who would know would be David Crosby of The Byrds … he just happened to be visiting in the studio that evening!)
Buffalo Springfield perform "For What It's Worth" on "Where The Action Is".