He played the acoustic into a cassette player and because he overloaded the cassette, it came out sounding electric because the cassette couldn't handle being driven like that. Then he'd take it to the studio and connect the cassette player to an extension speaker and mic that. That was the guitar sound of "Jumping Jack flash", "Street fighting man" and "Gimme shelter". All great guitar sounds. It's a good thing he captured them that way because soon after, they built cassette recorders with limiters on them so they wouldn't overload ! So those sounds are unique, never to be repeated ones.
I tried that once but it never worked because my cassette player never overloaded and when I sometimes pushed the acoustics into the red, it didn't sound good although I often, when in analog, pushed the acoustic and got good sounds. Unfortunately, my lack of mixing skill ensured that these weren't brought out.
One thing I do now and used to do then was record the acoustics, but then put them through effects like flangers, phasers and wah wah pedals and drive them a bit, with quite a bit of mid range upping. It completely alters the tone and timbre of the acoustic guitar, especially a 12 string. By playing with a capo and slowing or speeding up the recording to different keys and neck positions, when brought back to the original key, you can get some great sounds that no electric I've ever heard sounds like.
