If you’ve followed the instructions for using LilyPond as a command-line tool, as prescribed and needed by Karim Haddad’s omlily library, here:
You’ll find, and probably did find, that omlily won’t recognize it. Here’s the fix:
Go to the sources sub-folder of omlily, and open the lilypond-preferences.lisp file in a text editor. Where you read (at line 37):
(t (list :lilypond-path (pathname "/usr/local/bin/lilypond")))))
Replace it with:
(t (list :lilypond-path (pathname "~/bin/lilypond")))))
That’s it, you’re set.
All the best,