To pull this rockin' project off, Prado modified an old Nintendo Wii Guitar Hero controller. In his upgrade, mechanical switches were added as well as USB support with the help of a Raspberry Pi Pico.
According to Prado, you can use his project to turn anything into a Guitar Hero controller. It's built using Adafruit's CircuitPython, a fork of MicroPython, alongside a HID Library that enables the Pico to act as a USB keyboard and mouse. The Pico is wired to each of the fretboard buttons but it can also control the whammy bar (if your controller has one).
According to the original thread shared on Reddit, this was Prado's first time working with circuits and he already has plans to improve the design in the future. Be sure to follow him for more cool projects and upgrades to this one.