fix includeFromSong

include_from_song.ily

@@ -3,5 +3,13 @@ includeFromSong =
   (let ((noDefaultOutputBackup noDefaultOutput))
     (set! noDefaultOutput #t)
     (ly:parser-parse-string (ly:parser-clone)
-      (ly:format "\\include \"~a\"" filename))
+      (ly:format "\\include \"~a\""
+      (string-append
+        (dirname (dirname (current-filename)))
+        file-name-separator-string
+        "lilypond-song-includes"
+        file-name-separator-string
+        "liedbausteine"
+        file-name-separator-string
+        filename)))
     (set! noDefaultOutput noDefaultOutputBackup)))