Manual:LocalSettings.php

require_once("$IP/extensions/Score/Score.php");
 $wgScoreLilyPond = '/path/to/your/lilypond/executable'; /* required */
 $wgScoreAbc2Ly = '/path/to/your/abc2ly/executable'; /* if you want ABC to LilyPond conversion */
 $wgScoreTimidity = '/path/to/your/timidity/executable'; /* if you want MIDI to Vorbis conversion */
 $wgScoreTrim = true; /* Set to false if you don't want score trimming */