+ LILYPOND_VERSION=$(TOPLEVEL_VERSION) $(PYTHON) $(LILYPOND_BOOK) $(LILYPOND_BOOK_INCLUDES) --process='$(LILYPOND_BOOK_PROCESS) $(LILYPOND_BOOK_LILYPOND_FLAGS)' --output=$(outdir) $(LILYPOND_BOOK_FLAGS) $<
+
+
+# This allows -j make option while making sure only one lilypond-book instance
+# is running at the same time
+define CHAIN_RULE
+$(i)
+$(i):
+endef
+
+$(eval $(firstword $(MASTER_TEXI_FILES)): $(foreach i, $(wordlist 2, $(words $(MASTER_TEXI_FILES)), $(MASTER_TEXI_FILES)),$(CHAIN_RULE)))