Simple verse/chorus structure

freezepoint name: V5.1.0 (main)
Changes since last freezepoint (developer/mgr initials and brief description):
Previous significant freezepoint: V5.0.0
DHD20230704: can generate simple house intro/verse/chorus/verse/.../outro, for monthly data.
DHD20230629: initial place-holder chorus generator repeats first data melody bar, w/full tone range.