This is an ad, circa the late-1980s, for the AdLib Music Synthesizer Card, geared toward video games made for the PC. The company would be out of business by 1992, as the YouTube uploader tells us, having been replaced by Creative Labs Sound Blaster. But oh, just look at the expressions on this young boy's face as he's introduced to the glories of rich, goofy, synthesized computer sounds. Hilarious.
[h/t: Laughing Squid]