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

You can watch and listen to it on an Altair 8800b and get the octal object code for toggling into your own Altar here: => https://www.youtube.com/watch?v=fgYhVnmeWrk

PDP-8 music here => https://www.youtube.com/watch?v=vfx5H7ikA7Y

DECUS documentation entry for "PDP-8 MUSIC PLAYING PROGRAM" available on punch tape, 1976; written in assembly (PAL8) and fit in 4K words (12 bit word) of core memory. Worth a read. => http://www.pdp8online.com/miscdocs/DECUS/Decus%208-804_MUSIC...

I am not 100%, but i could have sworn that Woz talked about other members of the club playing around with something similar the day him and Jobs went there to show of Woz's would-be Apple 1.

I seem to recall reading about this running on minicomputers or mainframes, as described in another reply, and I also think this predated the Altair, as I first became smitten with computers around 1972.

Here's a video of a minicomputer generating AM radio music in 1971:

https://www.youtube.com/watch?v=akvSE5Z474c&lc=D5Mdy7u7Cxwsk...

I think that computer was built in 1971; the video mentions that the software used is Richard Wilson's player, which was written in 1975 (the DECUS entry is dated 2/11/1976).

I saw it done in the 1970s on a PDP-8 at the University of Minnesota. It wasn't just a couple of tones, it was playing complete songs. Later on a Z80 micro. Computers really emitted a lot of RF back then!

When I was a kid in the early 80's, I couldn't use my TRS-80 Model I during prime time TV hours. The main TV antenna for the house was located in the attic above my room. When I turned on my computer, the interference would essentially wipe out the VHF-Lo channels. Sometimes I would forget until I heard my parents yelling from across the house. Ah... good times...

For good tones, you had to get down close to "the metal." I recall that there were a few programs like this, but I believe they were written in assembler or machine language so as to control the cpu and bus directly.

Back then most programming for those machines was done at that level!

When I first laid eyes on the "High Speed Job Stream" in UofT's Sanford Fleming building (that particular building has since burnt down and been replaced), students were running jobs in PL/1, WATFIV, LISP, SPITBOL, COBOL, and many others.

In the labs, there were IBM Selectric terminals dedicated to APL.

And there was a BASIC dialect over at what was then "Ryerson Polytechnic." There was a room with terminals and acoustic couplers, no security to keep you out.

You need a username and password to use the terminals, but the username and password for each class was posted on a corkboard, so you would write your own programs as long as you didn't get in the way of actual students trying to finish their assignments.

I don't doubt that "most" programming was done in assembler, but there was no shortage of higher-level programming going on.

I said most programming for those particular machines. I agree that mainframes had largely moved on, and probably the larger minis too. My first exposure to programming was time-shared Basic in 1972.

You know, I think we've somehow fallen into _violent agreement_ on all subjects.

With the ZX81 and hardware of that era you kind of knew a lot more about what was going on with the radio waves as you would listen to a radio and have interference from television and computer kit, e.g. loading and saving programs off tape decks. The whole spectrum that was a bit more accessible with things like CB radio, nowadays we are deaf to analog signals and would not 'notice' and interference.