Add Contra Guitar to instruments.xml

[Jojo-Schmitz]

see discussion and request in https://musescore.org/en/node/90296

[mgavioli]

Not sure it really makes sense to add a tablature for an instrument with 'extra' strings and presumably no definite way to notate them...

[Jojo-Schmitz]

As far as I understand those extra strings are used open only (or not at all), so that would need to get ammended, I've missed that.
I guess otherwise tablatur would be the same as for a regular guitar, so, if at all, init from that?

[mgavioli]

No idea about the 'openness' of additional strings; the original requester may have some hints, though.

"I guess otherwise tablatur...": this is BIG "otherwise"! Tablature notation of strings below the 'standard' 6 ("bourdons") has been an issue for centuries, leading to many, different, ad hoc solutions; the current MuseScore implementation has been tailored on the most common ones attested in the literature; as there is no literature specific for this instrument, I doubt there is any 'default' bourdon notation for it.

If the users are happy with 'standard' (i.e. historically attested and common enough) bourdon notations for the lute, then ok; if not, I doubt tablature could be used for it.

[Jojo-Schmitz]

Well, there strings are open, in the sense that there are no frets, and as far as I understand they are not fingered fretless, but either just let resonating or plucked open. And for the latter the tablature seems to make sense, as with this it is possible to indicate which of these extra strings to pluck.

[Jojo-Schmitz]

OK, I've removed the Contra Guitar Tablatur, normal Guitar Tablature seems to be sufficient.