The trio of telepathically attuned interpreters who voiced the thoughts of the deaf mediator Riva of Ramatis III, each expressing a different side of his character.
Riva's chorus is made up of three people who have served him since childhood and who read his thoughts and speak them aloud. The ruling family of Ramatis III lacks the gene for hearing, and the chorus is a tradition that has grown up around it. One member voices the scholar and artist in Riva, one the warrior and lover, and the woman supplies the balance and judgement that hold the others together.
They appear in Loud as a Whisper, travelling with Riva on the Enterprise to Solais V, where two factions have fought for centuries. At the first meeting a soldier opposed to the truce opens fire and all three are killed.
Riva, left without any means of speaking, despairs until Troi and Data help him see another way. He stays behind to teach both sides sign language, so that they learn to communicate as they learn to talk to him.