Haha, a good idea for a thread.
Well, I don't have my first songs because we had no diskdrive, and after composing we had to save the file on tape-recorder. Those tapes are already lost in time.
The only thing I have, is a "song" (haha) made in 1989, for my pseudo-demo "True Music 1". It was made on ZX Spectrum 48K, for BEEPER only (1 channel, 1-bit quality, no volumes, square wave only) about 2 years before I bought an AY-interface.
http://yerzmyey.i-demo.pl/yerz-true_music1_1989.mp3
The curiosity is, it has been fully written in BASIC language (one note is one command
), and here is a part of a veeeeeeeery long listing, hahaha.

It took me hours to make this ultra-short crap, looped at the end. =8-D
I recently recovered it from my ancient cassettes with my ZX Spectrum programs.
The later songs had 2 channels and have been made on "The Music Box" editor. 