Adds alternative version with vocal parts only

This was achieved by

• copying the folder original_complete to vocal_parts_only
• removing parts
• removing instrumental staves
• removing cue notes

The score properties section in the README keeps note of which chorales were affected by these changes.

Furthermore,

• two of the three chorales that had four vocal staves have been reduced to two staves for homogeneity with the remaining ones;
• staff names have been homogenized.

Updates measure numbers

To make the measure numbers displayed in the scores comply with a wide-spread convention in music printing, all anacrustic measures have been systematically excluded from incrementing the counter. Likewise, second endings have been adapted so that their measure numbers comply with the a)-b) convention (i.e., in general, first and second have the same measure number).

A new column in the README table (Measure numbers) marks those pieces for which one or several measure numbers changed compared to the previous version of the corpus.

The original dataset

Scores as provided at https://gertim-alberda.com/chorales/ but converted to MuseScore 3.6.2 and fully extracted with ms3 2.5.1.