Repercussion (latinized form of "repeating" or "rebounding") is a special vocal singing technique consisting on singing a tone with a constant pitch.
The technique has been and is especially used in Gregorian chant[1][2] where repetitions of sounds are prescribed by certain neumes, such as a distropha or a tristropha.
The vocals are modulated in volume, without necessarily resulting in a pitch fluctuation, or a vibrato.
If the singing is not performed by a soloist, the singers modulate their voices in unison according to the direction of the cantor.
The perfect singing of repercussion requires vocal training and appropriate respiratory support.