The tinkle of piano keys. An unnecessary two-CD format. Couplets like “Feel like an antelope on a nature show/ Guess I gotta go.” It can only mean one thing: Nellie McKay is back.

This is no mean feat: McKay’s sophomore album, “Pretty Little Head,” was left in limbo after Sony/Columbia twice delayed its release and then dropped McKay altogether. On “Pretty Little Head,” McKay’s combination of honey vocals, tickled ivories and unremitting strangeness remains a mostly-charming cocktail. But something of her old zing has gotten lost.

“Get Away From Me,” McKay’s debut, played like pop from an alternate universe — one where cute girls sang about clones and dead cats and the boring stories that their Harvard-grad boyfriends told about Peter Lorre. It was sloppy, but that was its charm. Genuine, unaffected weirdness can be pretty compelling, and “Get Away From Me” was hard to get out of your head.

“Pretty Little Head” retains much of the same approach as McKay’s previous album — articulate, piano-driven cabaret pop. But this time around, the eclecticism is somewhat toned down. “Even has a rap/ clap, clap clap,” McKay sang on “Get Away From Me,” acknowledging her quirks with a shrug. On “Pretty Little Head,” she’s got — yes — another rap. She also has Cyndi Lauper, a banjo and one song entirely in French. But the overall package feels slicker, more streamlined — more like the work of a self-aware performer and a lot less like someone who’s incredibly talented screwing around in her bedroom.

This album finds McKay settling into a persona, rather than trying on musical and lyrical styles. The niche she’s chosen plays simultaneously off the stereotypes of the angsty singer-songwriter and of the fluff-ball pop star: What other album has songs called both “I Am Nothing” and “Cupcake”? Yet neither pose is quite ironic. McKay likes being angry and she likes being pretty, and she does both with a healthy dose of humor. In fact, it would seem that the only thing she has outright disdain for is blandness. And, of course, those who don’t share her views on animal rights. But her forays into political songwriting — such as “Columbia’s Bleeding,” about animal testing at Columbia University — tend to come off as heavy-handed and silly.

The best tracks on “Pretty Little Head” are as compulsively wordy and giddily melodic as ever. For instance, “There You Are In Me”: McKay’s voice and piano are equally nimble, their sprightly ease playing in contrast with the black lyrics. This may not be a subtle joke, but it’s a good one. The Cyndi Lauper collaboration, “Beecharmer,” is another a winner — Lauper and McKay’s back-and-forth has an easy charm. And the album’s first song, “Cupcake,” features lines like, “Anyone can toe the line, except for me, ‘cause I’m a disco dancer,” over a cluster of relentless hooks.

The record only really goes awry at the end, with the song “Mama & Me” and its rap dalliances. The song itself is tiresome and heavy-handed, and its spoken-word (and screamed-word, and whined-word) interludes call attention to McKay’s brattiness in a way that feels uncomfortably accurate. Cringe as you listen to its intervals of caterwauling, which then segue into the disastrous “Pounce”: “Pounce! Pounce!/ I’m gonna pounce!/ Like a PUSSYCAT!” This sequence encapsulates McKay’s worst tendencies. Grating, stilted and precious, it’s as if all that remains of her quirkiness is a caricature.

The real problem isn’t unpalatable weirdness, though; it’s that the album is too palatable. For somebody who once mocked Norah Jones’ easy-listening piano stylings, McKay has gotten pretty inoffensive herself — a lot of these songs wouldn’t sound out of place as muzak at Anthropologie. “Pretty Little Head” is enjoyable, but it’s hardly as engaging as the old, weird Nellie.