https://collectionsdumusee.philharmoniedeparis.fr/search.asp...
I see your added frets, and raise "add frets on the fly using Lego":
Really? I highly recommend Flying Microtonal Banana.
Really? Most people's first intro to microtonal guitar is recent and brought to them by Angine de Poitrine.
You only have to put your finger somewhere in between two frets to get a particular note, so you can play more than the tiny handful of chords that can be played on something like a violin.
There are non-fretted guitars but they are rare, and I think early banjos were not fretted.
What do you think double-stops are?
Of course in most music contexts there is more than one instrument playing and so the others can fill in the missing note making a full chord. Only a "one-man-band" really feels the loss.
That's E, G♯, B, D, F
https://www.youtube.com/watch?v=lz3WR-F_pnM
If not, stop and watch it. But make a cup of tea to enjoy with it first, and maybe put a cloth over your keyboard for when you inevitably splutter tea all over it.
in college a good friend was a very good Oud player (plucked, some number of strings.... more than 8? I forget), and it definitely sounds different from guitar due to less sustain. Clearer notes and chords, but they don't linger as long or loud.
Edit: apparently it's 11 strings? ok.
On a Cello a fingered string is gone in 2 seconds.