NOTATIO

Sounds good. I'm happy to check the SFD file for you.

thanks!
I PMed you right now.

Just retried.
In case it doesn't work again, PM me an email address where I can send the files...

did you receive the PMs?
I see them in my "Outbox" directory, and not in the "Sent messages"... so I don't know if the're been set or not

I got it. I won't be able to take a look until later tonight or tomorrow morning, though.

no problem, just wanted to be sure... take your time
I'm still experimenting with other glyphs...

I've worked through the files you sent me and there appears to be a handful of issues in this font. The GSUB subtable references glyphs that don't exist, so that invalidates then ENTIRE subtable. So, removing all references of non-existent glyphs from the lookup tables is the first thing to do. The second thing is to make sure the advance width of all glyphs is greater than or equal to zero.

I ended up removing all the other GSUB lookup tables except for "liga", fixing the advance widths, and then it worked "b 1 3 b13":
(Note that I had to add a bunch of spaces before the ligature so you could see it without colliding with the previous characters)

I'll PM you back the fixed file so you can do your own testing with it.

the backward shift is made on purpose.
In the font the only char that have a fixed width are the frets and some space chars.
All the symbols have 0 length and are shifted on the left so that you can overlap one on another, on the same preceding fret.
This way you can e.g. write a crossed note name in a square, or any other combination, using with only 4 glyphs.
I chose this operativity becuse originally I redefined the letter chars on the keyboard and there are not many available.
I'm exploring ligatures to overcome this limit, while maintaining the regular alphabet chars without having to switch font in the document.
About the invalid lookup tables: I downloaded the "Open Sans" font and added my glyphs. The problems are in the original file.
Maybbe I'll have to try to do the same with another free font, less cluttered...

I'm now experimenting with another version of the font that works in the opposite way: zero length frets, 0 lenght symbols, but shifted on the right... It works, but editing is less intuitive...

I figured the backward shift was intentional, given that so many glyphs were that way. Some of the left-shifted glyphs didn't have 0 width, but they all do now in the file I sent you.

All the original characters are still accessible, just not the non-"liga" GSUB lookup tables, so I don't seen any reason that you couldn't just keep moving forward with your current plan, but it's up to you.

ok, the OSC file has been installed, but the ligature in LO still seems not working...
maybe I'm doing something wrong, but I expected that the 'b13' glyph appeared after pressing 'b','1','3' ...
Maybe is my LO config to be investigated now?