-to the beam. If the stem is invisible (eg. on a whole note), the
-tremolo must be centered on the note.
+to the beam. If the stem is invisible (e.g. on a whole note), the
+tremolo must be centered on the note. If the note has a flag (eg. an
+unbeamed 8th note), the tremolo should be shortened if the stem is up
+and tilted extra if the stem is down.
+
+The tremolos should be positioned a fixed distance from the end of the
+stems unless there is no stem, in which case they should be positioned
+a fixed distance from the note head.
+
+If an impossible tremolo duration (e.g. :4) is given, a warning is
+printed.