Alright I got it working. This persons video was a big help in simplifying the topics and making sense of what I was actually trying to do.
For other electronics newbs like me who want to understand how to do this:
- Take power from somewhere (I just took it from the VDD on the Axoloti board) and connect it the collector pin of the transistor
- PWM from the axoloti goes to the base (middle) pin
- connect the PWM modified output from the emitter pin to the motor
- the other motor wire goes to ground of the power source
it worked without a resister, diode or capacitor in the circuit. They are probably important so I'm going to add them back in and try to learn why before I stop bread boarding!
Next steps are the axo patch, installing an input jack on the cassette player, and knocking up the full circuit on strip board.