“Meeting People Is Easy,” the 1999 documentary film that captured Radiohead at the grouchy height of their fame after the release of “OK Computer,” had exactly one scene in which the band’s lead singer, Thom Yorke, looked happy. Okay, one scene in which he didn’t look unhappy: Yorke seems incapable of joy. It wasn’t when he was on stage performing, and it certainly wasn’t when he was sulking in expensive hotel rooms or frowning at boneheaded questions from the press. It was while he was alone, bent over an electronic keypad, lost in oversize headphones and making music.

Yorke’s refuge from the world was really a chrysalis. After the dystopic majesty of “OK Computer,” Yorke led Radiohead into a hardcore electronic phase that left his band-mates scratching their heads and twiddling their thumbs for lack of ways to contribute. The resulting albums — “Kid A” and “Amnesiac” — abstracted every aspect of the Radiohead sound. Guitars all but disappeared, replaced by nebulous keyboards and jittering electronic beats. Yorke’s oncesoaring vocals were chopped, deleted, pitch-shifted, and otherwise kept earthbound. His lyrics seemed strung together at random: “Yesterday I woke up sucking a lemon / everything in its right place … there are two colors in my head / what is that you tried to say.” It was as though the world’s last great rock band had declared itself passé.

Much to the relief of fans, Radiohead has since reversed course. “Hail to the Thief,” their 2003 album, marked a return to the band’s old formula, and bootlegged live versions of songs from their forthcoming album — especially catchy numbers like “Bodysnatchers” and “Down Is the New Up” — suggest they’re pushing even further in the direction of unabashed rock.

But Yorke hasn’t lost his fascination with electronic music. It just lay dormant until “The Eraser,” his hermetic first solo album due out tomorrow on XL Recordings.

“The Eraser” gets off to a thrilling start. The opening title track finds Yorke singing in a melodic falsetto that’s surprisingly close to R&B — like Kraftwerk covering a Prince song. It is somehow both poppy and depressing. The bubbling effect is straight out of Missy Elliott. The lyrics sound, for once, like he’s singing to another person instead of shouting at the future: “I never gave you any encouragement / and it’s doing me in, doing me in.”

Several numbers might even be called love songs, although Yorke has an odd way of wooing. “Peel all your layers off / I want to eat your artichoke heart,” he sings to the pingpong beat of “Atoms for Peace.” He is more at home with the language of sci-fi, and here applies it to matters of the heart, with mixed results and metaphors: “No more going to the dark side with your flying saucer eyes,” he sings, “no more falling down a wormhole that I have to pull you out.”

This is not like Yorke’s earlier forays into electronic music, which essentially transferred Radiohead’s mopey grandeur to a new sonic environment. “The Eraser” is an album of intricate compositions that never strive for grand gestures. It is the sound of Yorke trying to sound small, a decision evidenced by the fact that he keeps his voice tightly reined in at all times.

And he manages to sound small. “Black Swan” is built on a catchy underwater guitar part that never really goes anywhere. “Cymbal Rush” begins with promisingly weird B-movie spaceship bleeps and bloops, but soon gets bogged down in marshy keyboards. “Skip Divided” is full of breathy sounds, foghorn-like music, and half-bored speak-singing; it ends up as a tame version of something Björk might have done on “Medúlla.”

There are other moments of promise, but none are fully realized. “And It Rained All Night” approaches the danceable herky-jerkiness of “Idioteque” from “Kid A.” It’s got a good beat, and Yorke raps to it — “it’s relentless, invisible, indefatigable, indisputable, undeniable, so how come it looks so beautiful, how come a man falls from the sky.” He then proceeds to deconstruct the drum track and warp the effects for a minute or so.

“Harrowdown Hill” is two very different songs overlaid on each other: one a sputtering drum and bounding beat straight out of the Gorillaz, the other defined by an eerie, wavering synthesizer. They never quite meld, but are saved by a great vocal melody in the choruses: “We think the same things at the same ti-i-i-me / we just can’t do anything about it,” Yorke sings, sounding every bit like a 1980s synth-pop star.

In the end, “The Eraser” serves mostly as a cautionary tale. This is where Radiohead might have ended up if Yorke hadn’t bent to the wishes of a band and a fanbase of millions. Fortunately, his fascination with electronic music has come full circle. It is once again a private refuge.