“I don’t want to be alone,” comes that all too familiar Billy Corgan cry from the abyss in “Tarantula,” the already heavily rotated first single from Zeitgeist (Reprise), the first album from the kinda, sorta reunited Smashing Pumpkins. It’s been almost 20 years since Corgan first bared his barren soul to the world — seven since MACHINA/The Machines of God (Virgin) signaled the collapse of the original incarnation of the ’90s alt-rock powerhouse — and not a whole lot has changed. Corgan assured fans of that when, on the very day his solo album The Future Embrace was released in 2005, he took out a full-page ad in the Chicago Tribune announcing the return of the Smashing Pumpkins. Perhaps that wouldn’t have been so comic if Corgan had bothered to ask his former bandmates if they wanted to regroup. But that’s not his style. Guitarist James Iha and bassist D’Arcy Wretzky declined. Neither contributed much to the Pumpkins’ studio recordings anyway: they were more like window dressing for the Billy Corgan Project — a suitably diverse-looking band in name only, built for mass consumption by the alternative nation.

It worked: the Smashing Pumpkins — or “The Mighty SP,” as the marketing machine behind the band has rechristened them — were one of the most successful alt-rock juggernauts of the ’90s. That reality bite was nearly lost in the wake of the cold, misguided digital mess of The Future Embrace, an album that had the once heroic Corgan playing to a more selective audience. Not even the empty buzz about a Pumpkins reunion could save that tour. But Corgan has spent most of the past two years working to rebuild his Smashing successes: D’Arcy’s been replaced by another hot blonde chick on bass, Ginger Reyes; and Iha’s role has been taken by another passable guitarist, Jeff Schroeder. Only Jimmy Chamberlin, the troubled but now clean powerhouse drummer, remains from the original incarnation.

It’s hard to pinpoint exactly when Corgan became so ridiculous. Mellon Collie and the Infinite Sadness (Virgin), the 1995 double album that cemented the Smashing Pumpkins’ legacy, was a grand, majestic alt-rock guitar symphony, wasn’t it? But somewhere between courting Courtney Love and replacing D’Arcy with Hole bassist Melissa Auf der Maur in ’99, Corgan devolved from a curious character into an oafish caricature. By the time he began appearing in that form-fitting black leather get-up for the 2000 Machina tour, he looked like an extra in the superhero spoof Mystery Men — the Black Plague, Mr. Melancholy, or Dr. Dismal. Did Corgan miss the Simpsons episode in which Homer thanks him for lowering Bart and Lisa’s hopes for the future, or did he just miss the subtext?

If Zeitgeist is any answer, he doesn’t care. The album is a testament to Corgan’s skill as a sonic architect: from the opening snare salvos that explode into the dense metallic churn of “Doomsday Clock” to the choirlike harmonies that hover over the funereal procession of “Bleeding the Orchid” to the ghostly guitars that haunt the desolate corners of the nine-minutes-plus “United States,” Zeitgeist is an impressive feat of studio engineering. But titles like “For God and Country” and “United States” promise more than just the same old self-obsessed brooding. Yet, in his efforts to prove he can still do it all himself, Corgan neglected to populate these huge cathedrals of sound, stacked high with guitars, with anything more than the echo of his own voice answering from across the digital divide. The chorus “We are stars/We are” (“Starz”) is as empty as it is desperate. And too often, Corgan’s lyrics read like a suicidal Dr. Suess: sure, he drops Kafka’s name in “Doomsday Clock,” but, at best, lyrics like “Please don’t stop/It’s lonely at the top/These lonely days/When will they ever stop” are Kafka for Idiots.

None of which makes Corgan a bad person. Zeitgeist is, as advertised, discomfort food for the ailing alternative nation. And it’s doing its job: the disc entered the US charts at #2, and is performing just as well abroad. Even better, “The Mighty SP” has reacted with uncharacteristic humor to a faux letter from Corgan that was recently published in the Seattle weekly The Stranger, proclaiming the greatness of the Smashing Pumpkins. An official response from “The Mighty SP” posted on smashingpumpkins.com suggests that the song “United States” was, “in its original form . . . well over an hour long and included a reciting of the Declaration of Independence narrated by all original cast members of the film Reality Bites starring Winona Ryder.” It also states that “8 out of 10 purchasers of the new album Zeitgeist have confirmed that they have experienced increased muscle mass after only two listenings.” Maybe that explains the bizarre white-caped crusader look Corgan’s sporting in the video for “Tarantula.” Either way, a little more humor would go a long way in the lonely world of Billy Corgan.