From the ALSA wiki
each time I use alsamixer I get into trouble with the meaning of :
- the two signs OO and MM : I never remember which means the channel is open and which mute.
Check for a little "MM" at the top of alsamixer's display. "MM" means the left+right stereo channels are muted. You can toggle muting on or off by pressing the "m" key.
- the names of the channels which are very esoterical.
- Could you explain them in a wiki page, such as PCM ?