Popular folklore has it that Link poked holes in his speakers to create this sound. He was the first guitarist to record a distorted sound and pretty much every rock guitarist afterwards copied it. He was also perhaps the first guitarist to use feedback musically, and also the first to use "power chords". A true innovator. This song features in the film Pulp Fiction. It's 50 years and 2 months old now.
Cheers, Tom.
