There's something inherently funny about the idea of Alice in Chains performing an unplugged version of their epic "Sludge Factory." And Alice in Chains are not a band who specialize in "funny." Since 1992, when they released the bone-rattling, soul-crushing Dirt, they've settled in as perhaps the heaviest, darkest, most oppressively downcast mega-rock outfit to scale the heights of Mount St. Grunge. Their metallic architecture of doom is usually fashioned from guitarist Jerry Cantrell's molten, bottom-heavy riffs, thundering drums, rumbling bass, and lyrics that delve morbidly into the horrors of heroin addiction, moody self-loathing, and plain old death. On one of their catchiest songs, "Down in a Hole," Layne Staley contemplates being buried alive. When he sings "Down in a hole and I don't know if I can be saved/See my heart I decorate it like a grave" in a wrenching, nasal-inflected wail, there's no trace of humor.

"Down in a Hole" is one of 13 tracks featured on the whopping 71-minute-long, surprisingly effective Unplugged that Columbia is set to release on this Tuesday. And though it reportedly took six takes to get things right when the session was taped for an MTV special in front of a select audience at the Brooklyn Academy of Music's Majestic Theatre back in January, "Sludge Factory" also made the cut. Bassist Mike Inez and drummer Sean Kinney slyly acknowledge the incongruity of performing one of their more densely churning numbers sans overdrive by leading into the tune with a short snippet of another heavy-rocker that's hard to imagine unplugged, Metallica's "Enter Sandman." (The joke is a lot funnier once you're aware that Metallica's James Hetfield, Lars Ulrich, and Kirk Hammett were all in the audience at the Majestic Theatre.)

Unplugged isn't the first time Alice in Chains have lightened their grunge-alloy payload. In fact, it's sort of in keeping with an AIC tradition that started with Sap, a four-song, mostly acoustic disc that came out after 1990's Facelift finally went gold in '92, and continued with Jar of Flies, an eclectic, post-Dirt EP that featured the jangly radio-friendly unit seller "No Excuses." Ironically, "No Excuses" ends up as one of the least compelling tracks on Unplugged. It really doesn't sound all that different from the original studio version -- which only emphasizes the absence of Cantrell's tasteful electric-guitar flourishes at the end of each verse. The same goes for Sap's soulful "Brother" and brooding "Got Me Wrong." Both were acoustically based from the get-go, so it's no big deal to hear them played that way again, though they both show that time and touring have taught Staley a great deal about how to use his powerfully clenched voiced in ways that don't resemble Axl Rose.

"Sludge Factory" and "Down in a Hole," on the other hand, are the kind of songs that take on a whole new dimension when you take away the Marshall stacks. And that is, after all, the point of this whole goddamn unplugged business. There's nothing special about Tracy Chapman unplugged or even Cowboy Junkies unplugged. (They were barely "plugged" to begin with.) But the massive howling bulk of Alice in Chains' "Sludge Factory" reduced to a strum-along campfire tune? Now that's something the alternative nation can sink its little teeth into.

Actually, the tunes on Unplugged retain much of their original weight even without extra amplification. There's just no way to diminish the gravity of those mournful baroque harmonies from Staley and Cantrell, which hang like a noose around the defiant hooks of "Down in a Hole" and "Rooster." And the grim, foreboding mood of a song like "Angry Chair" doesn't dissipate in the face of an acoustic guitar, so don't count on hearing it on your local AAA radio station anytime soon. But unplugging does accentuate the hymnlike quality and meditative tone of "Down in a Hole," "Angry Chair," and even "Sludge Factory," which features Staley emitting his spine-tingling imitation of a muezzin's wail over the slow-building intro. And if the test of a song's elemental quality can, as many have said, best be judged by how well it translates to an acoustic setting, then only the haunting "Frogs" comes up short -- though the electrified version of it on this year's Alice in Chains (Columbia) isn't all that compelling either.

MTV's Unplugged series has become a rite of passage of sorts for platinum-level modern rockers in the past few years. It's something we've come to expect from a band of Alice in Chains' commercial stature (and from aging rockers like Eric Clapton and Rod Stewart, who are looking to reconnect with a younger audience). For MTV, Unplugged is an opportunity to flex some industry muscle, to show that it can not only get the biggest bands to play but even induce them to leave their amps at home. For a group like Alice in Chains, it's an opportunity to prove their musicianship, even if it does take a few tries to get "Sludge Factory" right.