A singer is a person who uses his or her voice for musical entertainment.
A singer was featured in Chapter 14 of the The Big Good-Bye holonovel. After the USS Enterprise-E traveled back in time to the year 2063, Captain Jean-Luc Picard activated the program, where she was singing "Moonlight Becomes You", in order to trap two pursuing Borg drones. (Star Trek: First Contact)
During a Hirogen takeover of the USS Voyager in 2374, several members of the ship's crew were subjected to intense holographic simulations with all safety protocols disabled, one of which was set during World War II. Due to the use of neural interfaces, they each believed they were a character in the story, with Seven of Nine playing the role of Mademoiselle de Neuf, a resistance fighter posing as a singer at Le Coeur de Lion in Sainte Claire, France. (VOY: "The Killing Game", "The Killing Game, Part II")