Hey, thx for writing! So the Firefox issue is that the browser asks for microphone approval on every lesson, which can get a little annoying as a user. Is there a way to get Firefox to ask only once and remember what the user chooses?
To see what happens, try a few lessons in real guitar mode on our staging box. This box allows getUserMedia() even for FF:
So, this is known, and tracked in our bug tracker [1]. In the meantime, you can ask your users to use the drop-down in the doorhanger (the little panel that come down), they can whitelist your site this way (it says: "always share with this website" or something).
As you see in the bug (and in a duplicate [2]), this behaviour may change in the future. As you can understand, this need to be changed with care, it's rather easy to screw up, and could have serious privacy implication for our users (of course, your use case it absolutly legit, but websites get hacked, and some website are clearly malicious).
In general, if you want to talk to the team because you suspect a bug in Firefox, or anything, really, come in #media on irc.mozilla.org, or come and talk to us on the dev-media mailing list [3]. We don't bite, and love to hear about the crazy stuff people make with our APIs :-).
To see what happens, try a few lessons in real guitar mode on our staging box. This box allows getUserMedia() even for FF:
https://stage.getinstinct.net
(also just a heads up that our staging box is small, so if a lot of people hit it, it might get slow)