Octocky 8bit Improvo
A musical creation game from 1986 by Toshio Iwai, who created Electroplankton and most recently the Tenori-On for Yamaha. Octocky was released on the Famicom Disk System, the Japanese version of the 8-Bit NES console. The syncing of music, visuals and gameplay were groundbreaking at the time and it still stands out today. More information and a rom image to run in a suitable emulator are available here. Bonus review here.