V. A technical term used in multitrack recording; the practice of recording the same instrumental or vocal track twice and mixing the two sounds together to give them a "thicker" sound. The result is two almost-but-not-identical sounds being heard at the same, resulting in a subtle wavering effect.

One of the first recorded instances of this, and a good place to start to become familiar with the sound, is Buddy Holly's "Words Of Love."

cf. 4-track, Buddy Holly, his producer Norman Petty, The Beatles, legendary Motown producer Phil Spector, and "Norfolk Sound" guru Frank Guida