Keith Richards recorded using a Philips cassette recorder. In this article from the Wall Street Journal, he says,

Around this time, I became fascinated by one of the early cassette tape recorders made by Philips. The machine was compact, so it was portable, and it had this little stick microphone, which would allow me to capture song ideas on the fly. So I bought one, but as I watched the small tape-cartridge reels turn, I began to think of the machine not as a dictation device but as a mini recording studio. The problem is I couldn't use an electric guitar to record on it. The sound just overwhelmed the mike and speaker. I tried an acoustic guitar instead and got this dry, crisp guitar sound on the tape—the exact sound I had been looking for on the song.

At the time, I was experimenting with open tunings on the guitar—you know, tuning the strings to form specific chords so I could bang out the broadest possible sound. That's how I came up with "Street Fighting Man's" opening riff—even before I bought the Philips. I based the rest of the song's melody on the tone pattern of those odd sirens French police cars use [sings the siren and lyrics to illustrate].

Sometime in early '68, I took the Philips recorder into London's Olympic Sound Studios and had Charlie [Watts] meet me there. Charlie had this snap drum kit that was made in the 1930s. Jazz drummers used to carry around the small kit to practice when they were on the bus or train. It had this little spring-up hi-hat and a tambourine for a snare. It was perfect because, like the acoustic guitar, it wouldn't overpower the recorder's mike. I had Charlie sit right next to the mike with his little kit and I kneeled on the floor next to him with my acoustic Gibson Hummingbird. There we were in front of this little box hammering away [laughs]. After we listened to the playback, the sound was perfect.

Richards usage of a recorder is also documented in The Atlantic and in his autobiography Life

"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. [...]

In the studio I plugged the cassette into a little extension speaker and put a microphone in front of the extension speaker so it had a bit more breadth and depth, and put that on tape. That was the basic track. There are no electric instruments on "Street Fighting Man" at all, apart from the bass, which I overdubbed later. All acoustic guitars. [...] I wish I could still do that, but they don't build machines like that anymore. They put a limiter on it soon after that so you couldn't overload it. Just as you're getting off on something, they put a lock on it. The band all thought I was mad, and they sort of indulged me. [...]

"Street Fighting Man," "Jumping Jack Flash" and "Gimme Shelter" were all made just like that, on a cassette machine. I used to layer guitar on guitar. Sometimes there are eight guitars on those tracks. You just mash 'em up. Charlie Watts's drums on "Street Fighting Man" are from this little 1930s practice drummer's kit, in a little suitcase that you popped up, one tiny cymbal, a half-size tambourine that served as a snare, and that's really what it was made on, made on rubbish, made in hotel rooms with our little toys."