Doubling and Slap-Back

The doubling effect 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.

The related term slap back refers to the use of a single echo on a recorded track. The echo is often placed in a different spatial location in the stereo mix. Normally the echo delay is just large enough to be heard as a discrete echo on careful listening (e.g., on the order of tens of milliseconds). Compared to doubling, slap back uses a larger delay relative to the first voice, and the delay need not vary.

---

Previous: Variable Delay Lines
Next: Flanging

Order a Hardcopy of Physical Audio Signal Processing

---

About the Author: Julius Orion Smith III
Julius Smith's background is in electrical engineering (BS Rice 1975, PhD Stanford 1983). He is presently Professor of Music and Associate Professor (by courtesy) of Electrical Engineering at Stanford's Center for Computer Research in Music and Acoustics (CCRMA), teaching courses and pursuing research related to signal processing applied to music and audio systems. See http://ccrma.stanford.edu/~jos/ for details.