A continuous tone or chord is great source material for your Walkmellotron tapes. Record an entire side of a cassette with this tone or chord.
For this demo, I recorded a slightly de-tuned sine wave tritone I made with VCV Rack.
Hook up the audio out to headphones or an amplifier/powered speakers -- or even better through some effects pedals or outboard units such as reverb and delay.
Plug in the QT Py to a USB MIDI host/controller/sequencer or your computer/iOS device. Basically, anything capable of being a USB MIDI host.
I used a RetroKits RK-006 to pair the Walkmellotron with an Arturia Keystep MIDI keyboard.
Now, play any notes from MIDI 1 to 31 (A0 - G1). You can adjust the note range in code.py if needed, depending on the range of your MIDI controller.
Your Walkmellotron will play it's mellow/slightly haunting tones!