The mute keyword will toggle the mute setting for your Mac's audio. In other words, if the sound is not muted, invoking the keyword will mute it, and if the sound is muted, the keyword will unmute it.
An optional argument is allowed for the mute keyword, that represents the number of seconds to mute for; the sound will automatically unmute after the elapsed time. This can be useful for muting ads on streaming radio, for example.
There is also an explicit unmute keyword provided, in case it is easier for some to process that way (vs a toggle).
See the github page for source and more info, or just download directly.
Hope you find it useful!