This project intended to be an experiment on how cheap DIY musical cards can be. Jarv had in mind those that can be built at home. For his experiments he picked an Attiny85 microcontroller attached couple of piezzo speakers and powered with coin cell battery. That’s it with hardware part. And total cost reaches $5 limit.
Trickiest part of this is to port midi music information to MCU readable format. No one wants to pich each note by hand. By using python script he was able to convert midi to header file that can be included in to code.