The Game of Thrones theme performed on an 8-bit NES keytar by Youtuber Theramin Hero:
Most of the buttons are functional and can be remapped to different functions, as can the whammy bar. It also has an onboard arpeggio and drum sequencer.
The sound comes from the original RP2A03 chip in the NES, giving it that classic 8-bit sound. All of the available sound channels are utilised.
The software runs on a raspberry pi and is written in a language called Pure Data (pd). There are various modes including a midi controller mode as well as a standalone mode, which allows the whole instrument to be used with a battery pack.