The classic sound programs for the PDP-8 worked by executing instructions which caused electromagnetic interference (EMI) changes which when picked up by the AM radio produced sound. One program executed an instruction which caused a large EMI spike a the correct rate to generate the tones, another switched execution between two different core addresses.

The one I have reads notes from a file and can play chords. The quality varies the radio used, location, where tuned, and various other things. I think it can be better than the sample I have but I need to play more.

Some archive of songs and source are at ftp://metalab.unc.edu/pub/academic/computer-science/history/pdp-8/music/

More at ftp://ftp.dbit.com/pub/pdp8/nickel/music/

I also have an RK05 image of a DEC diagnostic pack with a music program and music files at ftp://ftp.pdp8online.com/images/os8/ file diag-games-kermit.rk05.

Samples of Beethoven 5th. Starts with the beginning of the song then I stopped the program and started the next song (the 5th third) loading. The strange sounds are the EMI from the computer while reading and processing a file from the RK05 drive. The .wav file is closest to the original sound but the others sound better with some of the high frequency removed.
As a .wav file () (Should work on windows systems)
As a .mp3 file () You may need to right click to download and use a special MP3 player.
As a .au file () (Sun, unix etc)

More to come later. More samples, hopefully better, more information. Possibly live playing from my machine. Email me suggestions below