Hello.
JavaScript I would guess this would work. Can't help you on that, I don't use javascript, though I do have it with my visual studio installation in case I decide to use it someday. From what I understand, you want to make a softsynth that runs in the browser, I've never seen this before, but I'm sure it's possible. You would have to supply a lot of sounds for various instruments, and for people who are serious musicians, you want to make the sounds very good quality.
Hth.
Guitarman.
What has been created in the laws of nature holds true in the laws of magic as well. Where there is light, there is darkness, and where there is life, there is also death.
Aerodyne: first of the wizard order