I am not sure if it is only JS libraries you are looking for (since it is an Electron app), but I released a fairly comprehensive python music theory library th

I am not sure if it is only JS libraries you are looking for (since it is an Electron app), but I released a fairly comprehensive python music theory library that not only supports Western tunings, but all sorts of equal temperaments. It even has some support for post-tonal music theory. https://xenharmlib.readthedocs.io/en/latest/ https://xenharmlib.readthedocs.io/en/latest/