The sing command will cause your character to sing the entered text loudly. Other characters listening will see the text displayed with occasional ASCII musical notes punctuating it, like this: o/`.
There are other ways to accomplish singing that may be more nuanced and beneficial for performance, including using poses, emotes and emoting loudly.
The quality of your singing is determined by your artistry skill and the stats that influence it, but there is currently no coded check for this, it's on the honor system. Please do not misrepresent the quality of your performances; they should accurately reflect your skill level.
SEE ALSO: help skills *Last Updated: 06/17/18 by Fengshui*