Like many an important pop composer, Paul McCartney has always been willing to blur the line not between artist and audience, or even between art and commerce, but simply between bad and good. Nowhere is that struggle more revealing than on McCartney II, by far the weirdest album the ex-Beatle ever made.

The genre-hopping home recording is loose, rangy, and deeply stoned: 11 songs--a far-reaching melange of Caucasian disco funk, straight-down-the-middle R&B, kraut leanings, electronic mini-symphony, and bedroom folk--rendered in an intimate, comparatively lo-fi mode. A man alone, making really fucked-up sounds. Absurd, fearless, and fascinating, McCartney II walks the thin line between genius and folly.

Strung up in Kraftwerk-y synthesizer chirps, furtive beats, throbbing bass drone, and incongruous acoustic guitar strums, "Temporary Secretary" is unabashedly grating, and features the boldest rhyming list of all time: "Belly dancer/true romancer, diplomat/girl like that, neurosurgeon/nothin' urgent." It also sticks in your head like a pick-ax.

But for every abrasion, there is a salve:

"Summer's Day Song" is fairy-tale English folk set to a Walter/Wendy Carlos-worthy analog synth odyssey so pastoral, you expect centaurs with pan flutes to emerge from the speakers. The obscure gem "Waterfalls" is also noteworthy, as it was cannibalized by R&B trio TLC for a hit a few years back.

The closer, "One of These Days," is trademark McCartney: a spare, plaintive acoustic ballad so simple, direct, and perfect in its construction you can't believe it hasn't always existed. It's the kind of song only he can write, and he has. But in the context of a semi-bedroom record, drenched in homemade reverb and delicately adorned with perfect harmony, the plain takes on an honest, humble beauty, absent on his bigger-scale studio albums.

You could only call it a masterpiece.