Doubling Simulation

Doubling is a studio recording technique often used to ``thicken'' vocals in which the same part is sung twice by the same person. In other words, doubling is a ``chorus of two'', where both parts are sung ``in unison'' by the same person. As an example, the Beatles used doubling very often, such as on the track ``Hard Day's Night''. A single variable delay line can simulate doubling very effectively.