patch 7.4.793
Problem:    Can't specify when not to ring the bell.
Solution:   Add the 'belloff' option. (Christian Brabandt)
diff --git a/src/if_mzsch.c b/src/if_mzsch.c
index 2135446..287ab1a 100644
--- a/src/if_mzsch.c
+++ b/src/if_mzsch.c
@@ -1569,7 +1569,7 @@
     static Scheme_Object *
 mzscheme_beep(void *data UNUSED, int argc UNUSED, Scheme_Object **argv UNUSED)
 {
-    vim_beep();
+    vim_beep(BO_LANG);
     return scheme_void;
 }