2011, Harry M. Benshoff, Dark Shadows, Wayne State University Press (2011), ISBN 9780814334393, page 38:This voice-over functions very differently from the extradiegetic narrator of the radio soap opera however, who tended to impose ideological coherence on the text, as well as serve as spokesman for the products being sold.
2011, Alison Peirse, "Horrible Women: Abjection, Gender and Ageing in Nip/Tuck", in Nip/Tuck: Television That Gets Under Your Skin (eds. Roz Kaveney & Jennifer Stoy), I. B. Tauris & Co. Ltd (2011), ISBN 9781845118624, page 76:However, in this sequence Colleen's actions alone do not make her horrific. Rather, the extradiegetic music condemns her.