Musicians :
Tim Hauser, Alan Paul, Cheryl Bentyne, Janis Siegel (vocals), Richie Cole (alto saxophone), Abraham Laboriel, Andy Muson, Chuck Domanico, David Hungate (bass), Jeff Porcaro (bongos, percussion, drums), Paulinho Da Costa (congas), Frank De Caro (contractor), Dean Parks (electric guitar), Greg Mathieson (electric piano Fender Rhodes), Dean Parks, Jay Graydon (guitar, gut string guitar, muted guitars), Paulinho Da Costa (percussion), Bill Mays, David Foster, Greg Mathieson, Jai Winding, Michael Omartian (piano, acoustic piano), Don Roberts (piccolo flute), Michael Boddicker, David Foster, Greg Mathieson, Ian Underwood, Jay Graydon, Michael Boddicker (synthesizer), Jimmy Wyble, Steve Lukeather (rhythm guitar), Don Roberts (tenor saxophone), Jay Graydon (additional vocals), Michael Boddicker (vocoder), Alex Acuna, Ralph Humphrey (drums)

This fourth album from Manhattan Transfer was the first for Cheryl Bentyne, who replaced Laurel Masse after the original singer's auto accident and subsequent decision to leave the group. Though replacing Masse was difficult, Bentyne's energy and style proved to be the perfect complement to the group's already dynamic performance. Hits from Extensions include "Twilight Zone" and "Birdland", which earned the group their first Grammy for Best Jazz Performance, Vocal or Instrumental.