I don't think I have seen this mentioned around, but you don't need an old ass computer with an OPL3 to use AdLib Tracker 2 anymore.
Some dutch guy has updated AdLib Tracker 2 to version 2.4.0 including support for MIDI input , which is pretty rad(lib), but he also has ported it to SDL so now it runs in Windows-based computers using an OPL3 emulator.
You can find the downloads here:
http://code.google.com/p/at2/
It's running great on my Win7 64-bit setup. This is pretty fantastic, as I am having issues with my Libretto that prevent me from using it properly. I can compose on my current PC and then transfer to the Libretto for proper sound output. Also now I can use version 2.4.0 as an FM module I can play with my MIDI keyboard.
official blurb:
Adlib Tracker II is, dare we say, the most userfriendly tracker aimed for the OPL3 FM-chip, and is full of advanced features to simplify your task of making the most of your Adlib-tunes.
Supporting 4 operator instruments, percussion mode, a wide selection of importable song- and instrument types and - maybe foremost - an advanced macro editor that can really push the FM-chip to the limit.
Last but not least, Adlib Tracker II's built-in MIDI support can turn this tracker into a full-fledged standalone FM synthesizer that can be controlled from your favourite DAW.