The biography of the Ohio-born singer-songwriter Scott Walker is a touchstone for fans of strange and difficult music. Walker, who turns seventy in January, recently recorded his fourteenth solo album, the severe and charged “Bish Bosch.” He began his career at thirteen, when he was billed, under his birth name, as “Scotty Engel, the baritone from Denver,” on a 45 called “When Is a Boy a Man.” Even then, his singing voice was deep enough so that the title was a reasonable question. The son of an oil-company geologist, Walker spent his childhood moving around the United States. In 1965, he reached London, where he still lives, as part of a trio called the Walker Brothers, none of them Walkers or brothers. For a brief period, the band was as popular in England as the Beatles or the Rolling Stones. After the dark but relatively traditional romantic pop music of that trio, Walker came out with a well-received quartet of idiosyncratic solo albums. In the seventies, he recorded a stretch of confusing commercial attempts, which were followed, in 1974, by a re-formation of the Walker Brothers. The four tracks that Walker wrote for the group’s final album, “Nite Flights,” gave him a chance to develop his extreme take on song form.

In the thirty-four years since then, Walker has produced only four albums: “Climate of Hunter,” “Tilt,” “The Drift,” and “Bish Bosch.” They are generally seen to represent the truer, or more serious, version of Walker. This is sensible. Walker’s songs are closer to European art songs than to any version of pop or rock, even though they typically feature cinematic string arrangements. For example, one track on his new album is a twenty-two-minute composition called “SDSS1416+13B (Zercon, A Flagpole Sitter),” which touches on the fates of both a dwarf and an astronomical phenomenon known as a brown dwarf. Over the past decade, Walker has asked musicians to create percussive textures by punching meat and scraping machetes.

But to conceive of Walker simply as someone who moved from pop to art is to hear only one channel of a stereo narrative: the paired signal is that Walker has always been idiosyncratic, and favored extremes from the start. That he appealed to teen-agers back in the twentieth century is something of a fluke. In response to his avant-garde solo album “Scott 4,” from 1969, a poem credited to “14 ex-Scott Walker fans” was printed in a British newspaper. The betrayed faithful saved the cruellest blow for the kicker: “Your reign is over—goodbye Scott / Face it man—you’ve had your lot!”

The hits that form the core of the Walker Brothers’ “straight” pop work are streaked with morbidity and exaggeration. The group’s signature song, “The Sun Ain’t Gonna Shine Anymore,” first recorded by Frankie Valli and a No. 1 hit for the Walker Brothers in 1966, sounds fairly threatening when sung by Walker. (Originally the trio’s bassist, Walker sang on one ballad and was then handed the task of heartthrob.) The song opens with a dark and awkward line: “Loneliness is a cloak you wear / a deep shade of blue is always there.” Walker’s voice makes this idea both smooth and lethal. As he says in “30th Century Man,” a documentary about his life, his baritone voice had the potential to “tranquillize” people. The impulse to work against that, and to wake people up, has been a defining characteristic of his songs. His performance on “The Sun Ain’t Gonna Shine Anymore” makes a decent trifle about missing a woman into an existential pothole.

Walker hasn’t performed live since the seventies, and he works slowly, but he is not a recluse. He speaks openly with reporters and works with collaborators. He wrote delightfully harsh music for Leos Carax’s film “Pola X,” from 1999. Anybody who has given in to the power of a Carax movie, like the recent “Holy Motors,” knows that the logic of Carax’s work is that of imagination; the films are guided by the same sideways motion of association that drives dreams. Walker works similarly. He has spoken repeatedly of dreams as inspiration; seen this way, his songs aren’t unusual. His lyrics don’t follow convention and parts often don’t repeat, and this mimics the structure of dreams. Though it has taken him more than forty years to master this process, he was one of the first pop artists to explore the possibilities of the irrational in the larger setting of pop music, abetted by a thorough understanding of traditional pop tools. To use David Byrne’s famous injunction, Walker began to “stop making sense” around 1978, with his work on “Nite Flights.” Surrender to Walker’s lyrics and his extreme sense of arrangement, and you leave the world of the mundane.

In a telephone interview, Walker told me that he typically writes lyrics, then composes the accompanying melodies on a keyboard, generating the sheet music with a software program. But much of “Bish Bosch” is silence punctuated by his voice. On previous records, he has needed an entire choir and orchestra to reproduce his visions; on the new album, he doesn’t require much help. If he wanted density before, now he wants a very specific backdrop for his voice—half nothing, half noise.

Most older former pop stars don’t stay this committed, and it’s hard, over the thrilling and baffling length of “Bish Bosch,” to guess why, and for whom, someone would record an album like this. Walker has explained that “Bish” is slang for “bitch” and that “Bosch” is like the painter, and so the album’s subject is a universal woman artist. It seems more apt to see Walker’s work as split into two halves: songs he has turned into nightmares and nightmares he has turned into songs.

The split seems to have taken place in the past decade. In Walker’s post-pop catalogue, there is a fairly clear line that runs from the perverse pop of “Nite Flights” through the long, demented songs of “Tilt.” These pieces have repeating rhythms, and sections that move like verses and choruses, no matter how obscure the lyrics. Something new, though, emerges on “The Drift,” from 2006, and on “Bish Bosch”: it’s a non-repetitive, sprawling kind of music that moves in fits and starts. That sounds forbidding, but these albums are more approachable than “Nite Flights” and “Tilt.” Freed from any obligations outside those in his head, Walker’s compositions travel more easily from idea to idea.

“Bish Bosch” seems like the least restrained representation of his night brain, let loose upon a budget generous enough to let someone find the perfect farting for “Corps de Blah.” There is slightly less of the intense string-section work that Walker has grappled with since he was a teen-ager. This time, the percussionist Alasdair Malloy, the drummer Ian Thomas, and the guitarist Hugh Burns carry much of the weight. They are appealing foils—Burns’s guitar is often like a second voice, high and impossibly unpleasant, and a sort of stage lighting for Walker, creating ghostly soft tones. Malloy is the one banging on things and wielding the machetes—in Walker’s new songs, timekeeping is rare but texture is vital.

During the song “Tar,” Walker repeats a phrase, as he does several times on the album. “Flat nose whistle goes up ahead” appears twice, like a fragment from a badly translated lullaby. It doesn’t create the motion of a pop song, but it does reduce some of the drift. Walker then twists the phrase into “thrushy-tongue lolling up ahead,” pushing words toward their own music. His voice works slightly above its regular register, and wobbles with vibrato, establishing and maintaining tension. A cast of people and animals move through the piece: “God creates animals and then man. Jackaroo in the slew.” As Walker says his words, Burns makes his guitar increasingly woozy and odd, leading into a burst of string cacophony and then a brief passage of what sounds like sweet concord. But it’s a classic Scott Walker moment—one sound becomes a palliative simply by being less intense than another. Discord soothes Walker the musician, so that Walker the writer can tell his stories.

But who will listen? When I asked Walker for whom he made these records, he said, “I suppose I’m doing it for myself . . . hoping to reach a lot of other me’s,” which is a pretty good definition of whatever pop isn’t.