MIDI Creator
Click or drag in a tune across as many instruments as you want — hold Shift while dragging to tie steps into one held note — then download a real .mid file, right here, without leaving Thagobyte.
Playback here is an approximation (a plain oscillator per note) so you can hear what you're composing — each track's instrument only changes the tone color slightly during preview. The real General MIDI instruments play correctly, each on its own channel, once you download the file and open it in a real MIDI player or DAW.