Since breaking onto the scene in the mid-’90s, Timbaland has been one of the most innovative and sought-after producers in hip-hop. His ability to mix an eccentric style of beat production with commercial sensibilities has allowed him to mold stars-to-be (Aaliyah, Ludacris) as well as contribute to efforts from money-making juggernauts (Snoop Dogg, Jay-Z).

Since then, Timbaland has sort of become the production equivalent of Nate Dogg as far as guest appearances go, and, with labels paying top-dollar for pimping privileges, who could blame him? But saying Tim puts out too many mediocre records is like saying Allen Iverson shoots too much — in the end, they both get the job done.

Unfortunately, this “good enough” approach has been an all-too-common characteristic of Timbaland’s work of late. His regrettable return to rapping alongside Magoo on 2001’s Indecent Proposal overshadowed an otherwise-ingenious streak of eastern-influenced beat-making, while Tweet’s Southern Hummingbird reeked of Ashanti-esque opportunism.

Timbaland returns to his bread and butter with longtime friend and collaborator Missy Elliott, with whom he up-ended the image of hip-hop femininity on Supa Dupa Fly. Aptly titled Under Construction, the album is an intermittently effective meditation on hip-hop clichés like keepin’ it real and shoutin’ out to dead homies that somehow simultaneously feels undercooked and overworked.

First single “Work It,” already a ubiquitous radio force, is destined to become the house-party anthem of the winter, with Missy’s lascivious crooning nicely accompanied by Timbaland’s booty-shaking beat and loopy synth effects. Missy then launches into a verbal shot at all the nay-sayers of her newly slimmed-downed physique with “Gossip Folks,” a track given an extra dose of dirty-South sass by Ludacris’ sticky tongue and Tim’s thumping bassline.

Missy’s new image seems to have given her a newly confusing disposition, though, as Under Construction uncomfortably stumbles between drunken dance-floor tracks and would-be elegies far too often. It certainly doesn’t help that Elliott chooses not only to bookend the album with trite diatribes about Aaliyah’s legacy and (surprise!) 9/11, but also intersperses her commentary between tracks just as the listener is getting into the groove.

Further complicating things is a conspicuous absence of the cheeky sexual humor that made Miss E. So Addictive such a breeze. In its stead she tirelessly trudges on about the glory days of old-school hip-hop — the fashion, the icons and (surprise … again!) emcees that settle their beef with words, not guns.

If that’s how Missy wants it, then Timbaland/Missy Elliott protégé Ms. Jade is dealing with more beef than a McDonald’s booth at the Wisconsin State Fair. Sporting a chip on her shoulder outsized only by her lyrical presence, Ms. Jade’s debut Girl Interrupted announces the arrival of what should prove to be the most formidable female presence in the rap game since Eve.

Timbaland has always shown a good ear for new talent, and he thunderously throws Jade into the mix on “Jade’s a Champ,” bolstering her raspy delivery with polyrhythmic percussion and nicely placed backup singing. “She’s a Gangsta” is a study in contrasts, with string arrangements and gritty flows that seamlessly go from cacophony to urban symphony.

Tim even ventures into new territories of beat-making by using layered, vocalized onomatopoeia on “Ching Ching,” a track made all the more refreshing by its lightheartedly funky twist on hip-hop materialism.

The album’s highlight comes on its requisite guest-spot from Jay-Z, in which he and Ms. Jade verbally dodge in and out of Timbaland’s syncopated shakes and samples. And look for Jade to provide Missy with some competition for that house-party anthem with “Big Head.”

In fact, just about every track in Girl Interrupted is a straight-up head-nodder. If the album ever falters, it’s when Tim’s beats are too spare for Ms. Jade’s raucous flow or too overbearing for her more subdued deliveries. But the fact that these tracks still come off as bangers is simply the sign of a young emcee trying to choose the right stylistic path with a producer not quite knowing which one of her hands he should hold.

Under Construction: C

Girl Interrupted: B