Music writer Polyphonic, who makes incredibly informative video essays on an ongoing basis, explained how The Grateful Dead‘s short-lived, but brilliant sound system known as the “Wall of Sound” changed the sonic quality of live performances from that point on. The Wall of Sound was the brainchild of audio engineer (and chemist) Owsley “Bear” Stanley, who only sought to make the sound as clear onstage as it did in the studio. The system was massive, made up of over 600 hi-fidelity speakers that sat behind the band as they played. Owsley worked with music company Alembic to find a way to avoid the usual microphone feedback.
They cracked it, putting a pair of microphones next to each other. One for the singer and one for the ambient noises onstage. That ambient noise was then fanned through an amplifier that subtracted it from the vocal microphone. In doing so, only the vocals came through and the feedback was removed. This is actually the same theory that would go on to be used in noise cancelling headphones.
Sadly, this incredible wall was taken down during the band’s brief retirement after their October 1974 Winterland show and was never put back together after that.