The cool thing about magnetic tape is that by varying the speed at which you read it, you can vary the pitch of the output. [Issac] decided to take advantage of this by running a sophisticated digitally controlled pitch mod on his Tascam Porta 02 tape recorder.
The build uses a Raspberry Pi Pico, which uses PWM to control the tape drive motor speed. This is achieved through the use of an NPN transistor driven by the Pico’s PWM output. This allows precise control of the motor speed, and therefore of the pitch.
Once that was settled, the project was fleshed out with an OLED display and a rotary encoder. These allow various patches or scripts to be run on the Pico, controlling the speed of the tape drive motor in various ways. With a little work, [Issac] was also able to create a function that converts MIDI note values to PWM values that determine different motor speeds.
The natural thing to do next was to put a tape with a looping sample at a set pitch and then vary it in a sequence controlled by the Pico. The 8 steps of the sequence can be set manually with the rotary control, and in the future, [Issac] even plans to add a real MIDI input, allowing the system to act like a monophonic synth.
If you prefer other routes to height-change shenanigans, check out this project. Video after the break.