When a user presses 'm' for 'mute' in alsamixer, then a string "MM" appears at the bottom of a volume control. This change makes it obvious to the user that "MM" stands for "Mute".

However, when a new user opens alsamixer after some software on his computer has (perhaps by mistake) automatically muted a volume control, the "MM" won't indicate anything obvious. Among other things, this makes it difficult for new users to debug issues with the auto-mute feature. The fact that the volume control can be at maximum, even when the control is muted, contributes to the potential for confusion. The problem would be solved if, for instance, the "Item: " string at the top of the alsamixer screen were changed to contain the word "(muted)" for muted controls. This way, users who don't have sound will see what the problem is when they open alsamixer.

(from https://bugs.freedesktop.org/show_bug.cgi?id=91781, edited)