Guy,

opinions will vary on this, but to me "Friends of acoustic music" as a subheading seems too long and also a little scary (as in "do I have to join?", "is it a members only club?" etc etc). Notto mention that "acoustic" itself can confuse - for example, do you mean that there will be no amplification? Or are you trying to imply a certain style of music? Different people will understand this differently.

As for the main name, ideally a single word - easier to remember, catchier, yet it must allude to what's to be expected there. How about:

Soundbox
Soundbooth
Earworm
Soundalike

Good luck with the venture!