Fix Schubert Erlkoenig:

[th-we]

• Dotted quarter tremolos are tuplets
• Corrected and completed @unitdur
• Corrected a tie that needs to be a slur
• Corrected measure number
• Corrected lyrics

This doesn't validate against the stable schema because of single-chord tremolos [edit: tuplets], those have however been legalized in this merged pull request.

One thing that confused me when looking at these tuplet tremolos – the guidelines say:

The <bTrem> element can be used as shorthand for a tuplet consisting of repetitions of a single note or chord. This kind of markup may be the result of an optical music recognition process in which complete semantics cannot be determined a priori. When used this way, the @num attribute on <bTrem> can record a number to be rendered along with the pseudo-tuplet. In spite of this capability, the <tuplet> element is preferred.

I read this as "don't use @num unless you're an OMR process." But when an OMR process recognizes a tuplet number on a tremolo, why can't it just wrap the <fTrem>/<bTrem> into a <tuplet> element? The only thing that comes to my mind is if in the Erlkönig example, the tremolo notes were notated without dots, but with an added "3" to indicate that they should be split into three instead of two. But in this case, <tuplet> would not work; both features would serve strictly distinct purposes.

However, are non-dotted tremolos with a 3 actually a thing?

[th-we]

Created an issue on the guidelines repo to discuss what I raised above.