I'm using Ubuntu Studio 13.04 on a Thinkpad T420s. I haven't customised the mute/volume scripts etc. The mute key mutes my audio but doesn't unmute it. When I run
alsamixer I see the effect of the mute key on alsa: it mutes both the "Master" and the "Headphone"/"Speaker" channels, but then on un-mute it only un-mutes the "Master" channel.
I can manually un-mute the component channels in alsamixer, and my sound comes back. But of course I shouldn't have to.
How do I fix it so that mute-unmute works via the key?
(My problem seems similar to question 118675 but not the same, and the accepted answer there doesn't affect my situation.)
(I was using older Ubuntu Studio 11.10 until recent upgrade, and the mute key was configured fine.)