+/*
+ This iterator is hairy. It tracks both lyric and melody contexts,
+ and has a complicated communication route, reading/writing
+ properties in both.
+
+ In the future, this should rather be done with
+
+ \interpretAsMelodyFor { MUSIC } { LYRICS LYRICS LYRICS }
+
+ This can run an interpret step on MUSIC, generating a stream. Then
+ the stream can be perused at leisure to apply durations to all of
+ the LYRICS.
+*/
+