Fans of Belle and Sebastian will always be defensive; indeed, that is part of the band’s chemistry. To like Belle and Sebastian is to put yourself in a weak position, a maneuver ratified by the band’s many allusions to Christianity. Their frankly twee songs imagine a life of truant afternoons enlivened by mild sexual transgression but suffused with hope for some kind of grace. The appeal of their famous preciousness lies in its open-handed vulnerability: “With a winning smile, the poor boy / with naivety succeeds,” frontman Stuart Murdoch sings on an early song, “Get Me Away From Here, I’m Dying.”

But “The Life Pursuit” (Matador), their seventh full-length album, confirms the band’s departure from this original posture. With their previous album, “Dear Catastrophe Waitress” (2003), the group abandoned the vulnerability of earlier work in favor of a muscular King’s Road campiness. The specific early influences of other Scottish bands like Felt and Heavenly have given way of late to Manfred Mann, T. Rex, David Bowie, and, incredibly, Stevie Wonder.

Like many bands, Belle and Sebastian began with a very specific tone but, upon achieving success, have reached out to a larger matrix of pop references. They risk becoming pop connoisseurs rather than pop artists.

Belle and Sebastian can now afford a large, professional band – they recently rerecorded their second album, as if to improve on their amateur days. The orchestral approach compromises Belle and Sebastian not because it is inauthentic, but because it signals a change in emphasis from lyrics to music. And what is interesting musically – the elaboration of a retro ’60s sound – tips the band toward irony.

Belle and Sebastian made their best music in 1996, when they released their debut effort, “Tigermilk,” and their finest album, “If You’re Feeling Sinister.” Murdoch’s signature anthem, “The Stars of Track and Field,” addresses a high school track star, a girl “with a following of innocent boys.” Shallow voiced, Murdoch grants her a Promethean role: “You liberated / a boy I never rated,” and goes on to chant “The stars of track and field, you are / The stars of track and field, you are,” cleverly describing the art-kid’s eventual triumph in terms of athletic persistence. The meek shall inherit the earth.

This archetype – of a teenage journal keeper’s struggle to evolve – begets a strange kind of blues. Warm trumpet solos and “Peanuts”-style piano characterize “If You’re Feeling Sinister.” Murdoch laments “the new tall elegant rich kids,” and apostrophes “Kid in the snow, way to go / It only happens once a year / It only happens once a lifetime.” Parents are never mentioned. Morally, Belle and Sebastian are pro-books and anti-school; they finesse an almost-majestic message of self-esteem, contrasting adolescent hopes with the faded-curtains pathos of an “Eleanor Rigby” vision: “Hilary went to the Catholic Church because she wanted information / The vicar, or whatever, took her to one side and gave her confirmation / Saint Theresa’s calling her, the church up on the hill is looking lovely.”

Belle and Sebastian began to wobble when Murdoch let his bandmates take control on “Boy With the Arab Strap” (1998) and “Fold Your Hands Child, You Walk Like a Peasant” (2000), though enough of the old, lispy, diaristic songs came through to please. It was 2001’s “I’m Waking Up to Us” that represented a true change of course, marking the premiere of the band’s renovated ’60s sound and, on the song “I Love My Car,” a complimentary vocal style, louche and acrobatic. The technical change signaled something deeper: Murdoch, who once sang as a young boy, was now singing as a grown man surprised by his own boyishness: “I love my car / I’ll admit today that I’ve gone too far / To enamor myself of my little motor car.”

The word “little” plagues their latest album. “There’s something in my eye a little midge so beguiling / Sacrificed his life to bring us both eye to eye,” Murdoch sings, shoehorning the words into the relatively winning melody of “Another Sunny Day.” Elsewhere there is a “little paw” and a kid “a little cool,” for whom “the tracksuits are old, and the hoody’s way too moody / For the kid with the will to funk.”

No longer very moody himself, Murdoch lets his band’s upbeat orchestrals muffle his lyrics, which belittle the childlike dream of grace of his earlier work. Always wry and self-conscious, Belle and Sebastian now sound downright arch. Their lyrics have shifted to match: New songs like “Funny Little Frog” and “Sukie in the Graveyard” embarrass earlier work like “Fox in the Snow.”

If cool is really a matter of empyrean preferment, as Murdoch used to suggest, the bright confidence of this album seems like a worldly distraction. It is no coincidence that “Dress Up in You,” the only sad song on this record, is also the best.

Several other tracks merit praise: “White Collar Boy” approaches the strutting energy of the previous record, and the unnaturally slow “Mornington Crescent” recalls some of Belle and Sebastian’s sweeter elegies. But “The Life Pursuit” seems most concerned, as an album, with the new territory explored in “Song for the Sunshine,” a rainbowdelic drag that may be the most unlistenable song in the band’s catalog.

“Dear Catastrophe Waitress” at least demonstrated a feline zest. “The Life Pursuit” fails to jive in the same way; it is a dud.

blytal@nysun.com