What these guys were using?
I would say a Mosrite Fuzzrite or a Maestro Fuzz Tone maybe...
Sure thing ''fuzzy but tight driven distortion'' doesn't match in my book
Instagram:@Stonefly_effects
The idea is to put a pick in one hand and a guitar in the other and with a tiny movement rule the world.>David Fair
This is one of the great mysteries of the fuzz world. The Music Machine used their own custom fuzz box, built by the band's bass player, Keith Olsen, who went on to be a big time (and I mean big time) engineer and producer: https://en.wikipedia.org/wiki/Keith_Olsen
So you might get close with a Fuzzrite or maybe a NuFuzz, but it won't be the same.
"With The Music Machine, the bands vision was to record & play looking & sounding like no one who'd come before. Our own look & our own sound!!.. Sean Bonniwell (lead singer/ songwriter/ bandleader), Keith Olsen (bass), Ron Edgar (drums), Doug Rhodes (keyboards), & myself all agreed...
Keith was already an engineer, & set about designing & building our own fuzzbox for our own sound... We also tuned way down to D or Db for a more gutteral overall sound... After The Music Machine, I switched to a "Fuzzface"