Hello, I am assuming that problems specific to FOMUS may be reported here. I just noticed that when using :treble-8dn with the make-instr structure, fomus generates invalid lilypond code. it writes \clef treble_8 instead of \clef "treble_8" as per: http://lilypond.org/doc/v2.8/Documentation/user/lilypond/Clef.html#Clef "The argument clefname must be enclosed in quotes when it contains underscores or digits." ./MiS