How to switch an AC signal on and off with a BJT?
A common and simple approach is to use a transistor such as a 2SD2704K in a circuit such as this one (as from this previous answer): 



The transistor I mention is notable in this application for having high symmetry (large emitter-base breakdown voltage),so it does not have to be used upside down like the above example, and the hFE is  very high (maybe 30x better than an ordinary BJT in reverse)  so it will mute better.