The PK-100 Electronic Keyboard was an unlicensed add-on released for the NES by Bit Corp. made in 1988. It would come with its own cartridge. Besides that, nothing else is known about it. However, a add-on like it called the Miracle Piano did get a release in North America also with its own cartridge as well as also having a Genesis variant. Unfortunately, trying to search up the accessory only brings up a most likely unrelated keyboard called the PK-200. There's no ROM of the cartridge out there neither.