The great thing about magnetic tape is that you can change the pitch of the output by changing the speed at which you run it. [Issac] He called his Tascam Porta 02 tape and decided to take advantage of it by implementing a fancy digital-controlled pitch mode.
The build uses a Raspberry Pi Pico, which employs PWM to control the speed of the tape drive motor. This is achieved using an NPN transistor driven by Pico’s PWM output. This allows accurate control of motor speed, and thus pitch.
With this sort, the project was created with an OLED screen and a rotating encoder. These allow different patches or scripts to run on Pico, controlling the motor speed of the tape player in different ways. With a little effort, [Issac] Was also able to create a function that converts MIDI note values to PWM values that determine the speed of different motors.
The next normal task was to put a tape with a looping pattern on a set pitch, and then change it in a sequence controlled by Pico. The 8 steps of the sequence can be set manually with rotary control and in the future, [Issac] Even plans to add a real MIDI input, which allows the system to act as a monophonic synth.
If you prefer another route for pitch shifting Shenanigan, check out this project. Video after the break.