With “Jumpin’ Jack Flash” and “Street Fighting Man” I’d discovered a new sound I could get out of an acoustic guitar. That grinding, dirty sound came out of these crummy little motels where the only thing you had to record with was this new invention called the cassette recorder. And it didn’t disturb anybody. Suddenly you had a very mini studio. Playing an acoustic, you’d overload the Philips cassette player to the point of distortion so that when it played back it was effectively an electric guitar. You were using the cassette player as a pickup and an amplifier at the same time. You were forcing acoustic guitars through a cassette player, and what came out the other end was electric as hell. An electric guitar will jump live in your hands. It’s like holding on to an electric eel. An acoustic guitar is very dry and you have to play it a different way. But if you can get that different sound electrified, you get this amazing tone and this amazing sound. I’ve always loved the acoustic guitar, loved playing it, and I thought, if I can just power this up a bit without going to electric, I’ll have a unique sound. It’s got a little tingle on the top. It’s unexplainable, but it’s something that fascinated me at the time.
— Keith Richards, Life.