ToDo: articulations, slurs and beams.
Simultaneous music wip.
More preparations for beams, slurs and articulations.
Articulations wip
More articulations and ornaments.
Fingering (technical notation).
ScaleDurations wip
This will not work yet for `\scaleDurations`,
because the fraction is not set in attribute `scaling`.
Addition to some of the comments.
Slurs
Staff changes
Lyrics wip
Lyrics wip
Better handling of sequence and simultaneous sections.
Restructuring BarMus classes.
Dynamics
fix #456

improve parsing of \\tempo
Lyric stanzas
More structural adjustments.
Continuing stanza.
ly.music doc improvements