This is what worked for me:
1. Download the GNU/Linux (actually generic Unix) version of Director Musices from Internet Archive
2. Download CMU Lisp (or your package manager might have cmucl)
3. Set the correct full path in the dm/lib/make-dm1-cmulisp.lsp file
4. Be in the dm directory, and do lisp -load $(pwd)/lib/make-dm1-cmulisp.lsp
5. When the menu is displayed, select option 2 and type in the full pathname of Lilypond’s MIDI output (*without* putting quotes around it, contrary to what the prompt seems to suggest)
6. If you get errors like “The value of PCL::NEW-VALUE is NIL”, keep entering 0 until you get back to the Director Musices menu
7. Select option 3 and type rulepalettes/default.pal
8. Select option 7 or 8 and type a pathname for the output MIDI file
9. Select q, and type (quit) at the Lisp prompt
An “expect” script could be used as a quick way of automating this, or you could go into the Lisp internals.
You can then use my Python hack to add pan and reverb to Director Musices’ output if your version of Director Musices doesn’t implement it already.
Python hack to add pan and reverb
Note that Director Musices may delete any expression information that Lilypond itself has added, so it is not advisable for use on pieces where Lilypond has many dynamic marks to play.
All material © Silas S. Brown unless otherwise stated. Linux is the registered trademark of Linus Torvalds in the U.S. and other countries. Python is a trademark of the Python Software Foundation. Unix is a trademark of The Open Group. Any other trademarks I mentioned without realising are trademarks of their respective holders.