The author mentions using OpusModus, noting that it is similar in the spirit of Symbolic Composer. OpusModus is primarily the work of Janusz Podrazik, who also happened to be one of the main authors of Symbolic Composer.

Janus is also the co-author of a very nice book on the fundamentals of composition with OpusModus. [1] The book also servers a nice introduction to Lisp as well!

[1] https://diastemastudiericerche.org/product/marco-giommoni-ja...