The Maestro Rhythm King MRK-2, an early analog drum machine from the 70s that Sly Stone called the “funk box”. He used it all over his classic album “There’s a Riot Goin’ On”. Click on the photo for a larger picture.
Here’s a free Maestro Sample Set you can use.
This article gives some more info on Sly and the Maestro, as well as other early drum machines.
And an article about what happened to Sly and what he is up to these days.
EDIT: Note there is the possibility that Sly used the Maestro MK IV, and not the MRK-2. A comment from matrixsynth:
I believe Sly used a Maestro IV – similar, but not the same beast. At least that’s what Sly biographer Jon Dakks once told me after I snagged my own beloved MRK-2.”
There is at least one comment out there that does say specifically he used the MRK-2, and most of the articles that talk about him and the Maestro use a picture of the MRK-2. It was, however, the most popular of all the models so they may just be putting up the picture that was easiest to find. Note the MRK-2 came out around 1970, right around when he got his new drum machine and was recording “Riot”. I am not sure when the MK IV came out… if you have info on that let me know!
EDIT 2: More from matrixsynth:
“FWIW: Kraftwerk used a Maestro Rhythm King back in the day. They apparently built trigger inputs for each button into the unit so
that they could trigger it either by the drumpads used by Wolfgang and Karl or by one of their customized Synthanorma sequencers. The drums on TEE were done this way.