My ZX81 had audio. The ZX81 was so badly shielded with its thin plastic case it would make nearby radios go crazy. You could tune a MW radio off-station, put i

My ZX81 had audio. The ZX81 was so badly shielded with its thin plastic case it would make nearby radios go crazy. You could tune a MW radio off-station, put it close to the computer and listen to code executing. It made different sounds depending on what loops it was in. That was how I was able to make "computer music" in 1981, by poking little "machine code" routines into RAM and running them to make "songs" come out the radio.