the pitch is altered to make the voice sound more like that of a fourth grader. Isaac Hayes voiced the character of Chef, an African-American, soul-singing cafeteria worker who was one of the few adults the boys consistently trusted. Hayes agreed to voice the character after being among Parker and Stone's ideal candidates, which also included Lou Rawls and Barry White. Hayes, who lived and hosted a radio show in New York during his tenure with South Park, recorded his dialogue on a digital audio tape while a director gave directions over the phone, after which the tape would be shipped to the show's production studio in California. After Hayes left the show in early 2006, the character of Chef was killed off in the season 10 (2006) premiere "The Return of Chef". Guest stars Celebrities who are depicted on the show are usually impersonated, though some celebrities do their own voices for the show. Celebrities who have voiced themselves include Michael Buffer, Brent Musburger, Jay Leno, Robert Smith, and the bands Radiohead and Korn. Comedy team Cheech & Chong voiced characters representing their likenesses for the season four (2000) episode "Cherokee Hair Tampons", which was the duo's first collaborative effort in 20 years. Malcolm McDowell appears in live-action sequences as the narrator of the season four episode "Pip". Jennifer Aniston, Richard Belzer, Natasha Henstridge, Norman Lear, and Peter Serafinowicz have guest starred as other speaking characters. During South Park's earliest seasons, several high-profile celebrities inquired about guest-starring on the show. As a joke, Parker and Stone responded by offering low-profile, non-speaking roles, most of which were accepted; George Clooney provided the barks for Stan's dog Sparky in the season one (1997) episode "Big Gay Al's Big Gay Boat Ride", Leno provided the meows for Cartman's cat in the season one finale "Cartman's Mom Is a Dirty Slut", and Henry Winkler voiced the various growls and grunts of a kid-eating monster in the season two (1998) episode "City on the Edge of Forever". Jerry Seinfeld offered to lend his voice for the Thanksgiving episode "Starvin' Marvin", but declined to appear when he was only offered a role as "Turkey #2". Music Parker says that the varying uses of music is of utmost importance to South Park. Several characters often play or sing songs in order to change or influence a group's behavior, or to educate, motivate, or indoctrinate others. The