-EXTRA_DIST_FILES +=$(TELY_FILES) $(LY_FILES) $(ITEXI_FILES) $(ITELY_FILES) $(ILY_FILES)
-
-TEXI2PDF_FLAGS += -I $(top-build-dir)/$(outdir)/lys/
+# prerequisites for all rules invoking compiled lilypond binary
+ifeq ($(LILYPOND_EXTERNAL_BINARY),)
+INIT_LY_SOURCES = $(wildcard $(top-src-dir)/scm/*.scm)
+SCHEME_SOURCES = $(wildcard $(top-src-dir)/ly/*.ly)
+endif