The Apple II’s eight expansion slots on the motherboard were one of the most crucial features. These allowed consumers to add cards from Apple and several other vendors that immediately sprung up.

[Oliver] has been working in the area since 2021 with one [Glenn Jones], with the duo experimenting with connecting the versatile microcontroller directly to the slot bus of the Apple II.

With the card installed in Slot 7 of the Apple II and the DAC wired through to the synth’s CV/gate, it’s then a trivial matter of writing POKE statements in Applesoft BASIC to control the synth.