Crimp is a style of apparently improvisational singing and chanting with nonsensical lyrics. There is no musical accompaniment, as it is sung a capella.
It is performed by two or more people; the skill, therefore, is in managing to improvise exactly the same lyrics as your partner. Howard and Vince occasionally crimp, sometimes when reminiscing, and sometimes simply for the sake of it. Crimps range in length from around twenty seconds to several minutes.
Crimp has appeared in the radio series, all three television series, and the live show, although the style was not given a name until Series 3, Episode 3, in which the plot of the entire episode centred around the singing discipline.
Crimping was also mentioned in The Big Fat Quiz of the Year 2007, where presenter Jimmy Carr challenged Noel Fielding to crimp with Jonathan Ross. They then performed parts of Soup Song, although they alternated lines, instead of the usual unison style.