CREEPINGNET'S WORLD
VOYETRA SEQUENCER PRO
One method of writing your own music for vintage PCs, is to use a MIDI Sequencer, which leverages the FM Synthesizer found on sound cards such as the SoundBlaster Series, Windows Sound System (some standalone cards), and the Gravis Ultrasound, or even just funneling everything through a hardware synthesizer over MIDI/MPU-401.

The only "Big Box" piece of software in my collection to survive without being e-bayed is the SoundBlaster MiDi kit - which is a "kit" that contains Voyetra Sequencer Pro for DOS - a MIDI Sequencer program - a game controller passthrough with MIDI in/out plugs for a Synthesizer to use both to the used as a playback device, and as a controller (uses the gameport on your Multi I/O or sound card), and a huge manual.

This page deals with music composition, MIDI Devices using the older version of the MIDI interface, and composing music for computer games in *.MID format (MIDI).