(CNN) -- Alf Clausen never knows what to expect.
Alf Clausen has been scoring episodes of "The Simpsons" since the show's second season.
Sometimes it's an arrangement of a classic melody, such as the theme to "The Great Escape." Sometimes it's a parody of a show tune, such as "The Monorail Song" (a "Music Man" pastiche) or several numbers from "My Fair Lady." Sometimes it's an original piece, such as "The Stonecutters Song." Sometimes it's basic instrumental interludes.
And sometimes, it's all of the above. After all, we're talking about "The Simpsons."
But perhaps the biggest challenge facing Clausen, who has scored the show for 18 of its now 19 seasons (the 19th begins Sunday), is time. He doesn't get much -- during the season, about a week to write and record the musical cues. Watch a slide show of Clausen and his work »
Clausen -- a veteran composer and music director who has worked on "ALF" ("no relation," he's quick to say) "Moonlighting," "Police Story" and several films -- wouldn't have it any other way.
"The show is still really interesting," he says in a recent phone interview from Los Angeles, where he was working on "Treehouse of Horror 18." "I don't think I've ever been on a series where I walk into a music-spotting session never knowing what to expect. As a television composer, in the past I could spend a few weeks on a series and kind of get a drill for the way the score is supposed to be done. ... You can't do that with 'The Simpsons.' Every episode is a new surprise." Interactive: "Simpsons" 101 »
Clausen's most recent work is showcased on a new "Simpsons" CD, "The Simpsons: Testify" (Shout! Factory). The disc contains, among its 41 (!) cuts, "Everybody Hates Ned Flanders" (featuring David Byrne), the "My Fair Laddy" medley (from an episode in which Lisa attempted to remake Groundskeeper Willie), the "King of Cats" Itchy & Scratchy medley and "The Very Reason That I Live," another showstopper for Kelsey Grammer as Sideshow Bob.
Grammer is a particular favorite, says Clausen.
"He is so great. He's just amazing," he says. "You can tell he has this love of musical theater and he has the vocal instrument to go with it, so I know whatever I write is going to be sung the way I've heard it."
Clausen got his start in television almost three decades ago. After a childhood in North Dakota and a college major in mechanical engineering ("nobody knew one could make a living at music," he says of the time), he got a job as a professional musician and later studied at Boston's Berklee School of Music. Upon graduation in the late '60s, he lit out for Los Angeles, where he did jingles and variety shows (including "Tony Orlando & Dawn" and "Donny and Marie").
One job led to another, but as often happens with the business, Clausen found himself at loose ends when his show was canceled. A friend mentioned that a rather new comedy called "The Simpsons" was looking for a composer. Was Clausen interested in doing an animated comedy?
Clausen was not -- "I wanted to get more into movies of the week and feature films as a drama composer" -- but he went for an interview with "Simpsons" creators Matt Groening and Sam Simon anyway.
"Matt said, 'We look upon our show not as a cartoon, but as a drama where the characters are drawn, and I'd like it scored that way,' " Clausen recalls. His audition assignment was the first "Treehouse of Horror."
Now Clausen is a regular, with a steady -- if occasionally frantic -- workweek. As scripts are developed, he'll meet with the writers to see if they have certain ideas in mind that would require special music. Meanwhile, he has a regular meeting with producer Al Jean and other staffers to go over an episode, scene by scene, noting the spots that will contain music.
There are usually 30 to 35 cues per episode, he says -- more than one a minute -- and may contain music the show has licensed (which Clausen needs to arrange for his 35-piece orchestra) or emotional prompts.
"It's a pretty tight deal," he says. There's a week to create the compositions and arrangements, a recording session on Friday, mixing early the next week and then on the air Sunday.
Fortunately, Clausen finds it easy to get into the spirit of the show, with its loving parodies of musical styles. "I have a very, very deep love for Broadway musicals," says Clausen, "and I'm a big jazz lover, a big-band lover, I like contemporary classical works." He also gets to use his own orchestra, called (naturally) the Alf Clausen Orchestra.
His work hasn't been unnoticed: "I've had music teachers come up to me and thank me for keeping the sound of the live orchestra in front of students on television," he says.
Ironically, given the way the show is produced, Clausen has little contact with the main voice cast or some of the guests. ("When it's time to record the cast, I'm busy doing a score," he says.) But there are the perks. Clausen's gotten to conduct a session with the late Tito Puente, as well as do a session with Bono and U2, who sang Clausen's song "Garbageman."
And if you're going to compose, there are worse places than "The Simpsons," which probably will be airing Clausen's work in reruns for decades to come.
"There's a lot to do. I don't think I've ever seen a job quite as demanding on a composer-songwriter as 'The Simpsons' is," Clausen says. "But it's all very healthy, so I have no problem with it." E-mail to a friend