In 1976, Atari released the Atari Video Music. The AVM was a early sound visualizer that you would plug into your stereo and television. When you would play music, you would see a visualization of it on your TV screen. This is a normal function of music players today, but in the 70s this was cutting edge, even if the graphics were not:
DEVO trivia: An Atari Video Music can be spotted in the background of the music video for “The Day My Baby Gave Me A Surprise”.
The AVM was not very popular and was only manufactured for a year before being discontinued, so if you are lucky enough to find or have one, treasure it.