I think you are referring to "Foot on the Hill" being played on that Altair 8800, which cunningly made use of the radio frequency interference/ static controlled by the timing loops by the program - created by Steve Dompier .

Bill Gates was confounded and astounded, and described it as, "the best demo program I've seen for the Altair…". He could not figure out how the computer could broadcast to the radio.

You can read more about it here => https://en.wikipedia.org/wiki/Open_Letter_to_Hobbyists