Update, clean, and complete TabMEI documentation

[reinierdevalk]

What?

This issue lists information about the modelling of lute and guitar tablature that we might possibly want to include in the documentation - for example because it explains specific choices.

Example encodings

Lute tablature fragments:

• Italian tablature example: da_crema-1546_10-no_6 (= gerle-1552_1-no_4)
• German tablature example: gerle-1552_1-no_4 (= da_crema-1546_10-no_6)
• French tablature example: phalese-1546_20-no_2 (= milano-1546_6-no_8)
• Italian tablature example: milano-1546_6-no_8 (= phalese-1546_20-no_2)

Guitar tablature fragments:

• slurs example: van_halen-hot_for_teacher
• slides example: satriani-not_of_this_earth
• combined slurs + slides example: satriani-ice_9
• various techniques example: van_halen-panama

General

• Obvious errors (or editorial changes) are corrected (or realised) using a <sic>...</sic> element pair followed by a <corr>...</corr> element pair, so that all information remains in the encoding.

Lute tablature

• @dots='<n>' should go to the <tabGrp>: the dot applies to the rhythm (which gives rise to the symbol).
• n-line staves (where n != 6) are handled using @lines='<n>' in the <staffDef> (see, e.g., phalese-1546_20-no_2, where a five-line staff is used).

Guitar tablature

• We use @dur (rather than @dur.ges) in the <tabGrp> - the duration is unambiguous here.
  • DL: OK, my guess for why we did this: it's inter-chord interval, not duration. I can happily argue either way for this, and it might be worth revisiting in the SIG.
  • RdV: I thought the issue was that in the lute tablature the actual duration depends on interpretation (does |\ mean quarter note? half note?), while in the guitar tablature it is actually directly given in the CMN staff above (so no interpretation/ambiguity)?
• In the case of muted notes, the tab.fret value is deduced from the CMN staff above.
• ‘Single-note hammer-ons’ (see satriani-not_of_this_earth, m. 2; van_halen-hot_for_teacher, m. 2, 3): <slur> notes can have no @endid (cf. one-note slides) because they are 'single-note hammer-ons': notes not played with the RH but sounded by hammering 'out of nothing' a LH finger onto the fretboard. @show.dirmark='true' must in these cases always render 'H'.
• I left @startids referring to non-visible notes (i.e., notes just before or after the fragment) in for now (I assume that they won't break the parsing but just give a warning) (see satriani-ice_9 and van_halen-hot_for_teacher).
• Guitar tablature can have above the staff
  • No rhythm symbols (the rhythm indication is done in the accompanying CMN staff; see, e.g., all guitar examples in this repository). In this case, only <tabGrp> elements need to be used.
  • Rhythm symbols (see, e.g., https://nationalguitaracademy.com/guitar-tabs-for-beginners/). In this case, <tabGrp> elements with child <tabRhythm> elements must be used.
• Place attributes as 'high' as possible. E.g., on the <tabGrp> should go
  • @dur
  • @dot
  • @tie
  • @show.fret='true' @show.fret.enclose='paren'
• We must make sure that tied notes that are not repeated between parentheses in the tablature (which are usually found in the middle of the bar, and have the attribute @tie='m' or @tie='t') are not shown.
• There should be a default dirmark (default text for a technique) that is shown when @show.dirmark='true'. Candidates:
  • sl. for <gliss>
  • pick sl. for <gliss> with @pick-slide='true'
  • H or P for <slur> (hammer-on or pull-off)
  • T for <dir> with @technique='tap-fing' / @technique='tap-pick'
  • P.M. for <dir> with @technique='palm-muting'; followed by a dashed line in case of multiple notes
  • let ring for <dir> with @technique='let-ring'; followed by a dashed line in case of multiple notes
  • rake for <dir> with @technique='rake'
  • Fdbk. for <dir> with @technique='feedback'
  • w/ bar for <vibrato> with @technique='vibrato-arm'
  • Harm. for <dir> with @technique='natural-harmonic'; followed by a dashed line in case of multiple notes
  • A.H. for <dir> with @technique='artificial-harmonic'
  • T.H. for <dir> with @technique='tap-harmonic'
  • H.H. for <dir> with @technique='harp-harmonic'
• Bends are always indicated with text only rather than with @show.dirmark='true', as the @dis is indicated in semitones
  but the text may differ (additionally, at @dis='2', there is the option for either 'Full' or '1').
• Additional information can be added as text, e.g.:
  <dir technique='feedback' startid='#ID' show.dirmark='true'>Fdbk. pitch: D</dir>
• On using @show.dirmark='true' in combination with text:
  • @show.dirmark='true' in combination with text results in the default dirmark and the additional text.
  • @show.dirmark='false' in combination with text results in the provided text as dirmark. (TODO: Problem in van_halen-panama.mei at notes m4.n6-7: <pitchInflection> takes disposition as text, so what to do with the 'trem. bar' in the source?