Holly Brewer, of Humanwine, performs at The Paradise in Boston in 2007. The band headlines Thursday at the opening night party of the Boston Underground Film Festival. (Photo: Sushiesque)

The Boston Underground Film Festival — which takes place entirely in Cambridge — has a brilliant opening-night party planned for Thursday: a four-band steampunk party at T.T. the Bear’s Place.

The “steampunk” description is an umbrella the bands can gather beneath, but don’t expect a commitment to staying dry. They can no more be considered steampunk than easily reduced to any other term, which makes each a good match for the eclectic film crowd.

While none of the bands can be pegged in a specific genre, Humanwine (the band that performs last and is usually, sorry, referred to in all-caps) especially delights in subverting expectations. Not just in vaulting between musical styles from song to song, but in cheerfully pausing between songs for banter or to debate what to play next, or taking several minutes to discuss earnestly the best way to donate money to Haitian earthquake relief. Their connection with fans, skill as musicians and gift of Holly Brewer as singer has brought major labels around, but Humanwine has turned them away.

Mali Sastri, of Jaggery, performs in December with Christopher Barnes at the Cloud Club in Boston. Jaggery performs second at the film festival’s party. (Photo: bdjsb7)

Expect OwlWatcher to kick things off with the hardest rock of the night and Jaggery to do its thing, too: Bringing the room to a breathless pause. There’s something about Jaggery’s music — a gothic, operatically intense mélange incorporating keyboards, harp and viola — that tends to freeze an audience where it stands like, well, like the kind of people who refuse to stand under umbrellas and instead raise their heads, close their eyes and let the rains wash over them. Jaggery audiences go silent and still like people appreciating raw, scary, beautiful wildlife. They want to feel what singer-songwriter Mali Sastri feels when she writes and performs. They want to not miss what she does with her voice.

Probably the easiest comparisons are with Kate Bush and Tori Amos, but those are only starting points. As Morphine did decades ago in creating low rock, Sastri has had to come up with her own somewhat tongue-in-cheek suggestions to define what she does: Darkwave jazz? Siren rock? Whatever it is, it’s also a great lead-in to a band that, if anything, is even harder to describe.

Joanna “JoJo” Lazar and Edrie Edrie, of Walter Sickert & the Army of Broken Toys, perform in July at the Lilypad in Cambridge. Photo: bdjsb7)

Walter Sickert & the Army of Broken Toys is a rollicking, raunchy sideshow of jolly, wheezing menace and delight — a band like the best horror films that make you giggle with terror, a band with the same spirit as the New Orleans marchers whose most spirited tunes are played for the dead. They roll in with their burlesque dancers, leers and winks and Hieronymus Bosch tableaus of living mannequins and props and while they play you accept decay, laugh at sex and revel in life. When they roll out again you feel empty.

Part of that is because it’s an army, a troupe. When they leave, it’s like the circus is leaving, and you want to go with them.

It wasn’t always an ensemble. Walter Sickert and Edrie Edrie have been performing together for four years, but it was only when they were confronted with the massive stage at the last Mayfair in Harvard Square that they decided “I don’t really want to stand out there in front of 10,000 people by myself,” Edrie said. “So we asked some friends to join us, and then we kind of organically grew out of that.”

“If you ask how many band members we have, yesterday I came up with an official headcount. It’s a queer eight,” said Joanna “JoJo” Lazar, the burlesque poetess that started with the band as comic relief and has come into her own as a ukulele player. “‘Queer eight’ means anywhere between three and 15, on average.”

That includes “bunnies,” the performance artists rather than musical artists, who populate the stage, dance around it or sometimes invade the audience. Edrie will also make her way among the watchers and even sit among them to play for a while.

Obviously, you have to see them live to appreciate them. Even the Army’s most recent recorded material — a concept album called “28 Seeds: The Last Radio Show” created for the RPM Challenge — doesn’t come close to the charge you get from a show. (Edrie says an “amazing” album that might come close is due out in June, produced by the painstaking Lainey SchoolTree, and there’s an actual live album due in October.)

Among other benefits of the live show is the cathartic “Off With Her Head,” in which Edrie splits the audience and exhorts half to scream “head” and the other half to scream “off” in an orgiastic contest in which everyone wins; and a “Ghostbusters” cover that works so winningly you (appropriately) get shivers.

The band is touring in June and already looking forward to returning to First Night, Edrie said, where room was made last year even after the schedule was fully booked. Their sets went phenomenally well, toned back only slightly in deference to the children who were attending. The energy, the band members said, was amazing, as was the connection with the families, old and young.

“It’s not strange, because I think we’re all emoting a whole lot of shit we’ve been carrying around since childhood, and I mean that in the exuberant, fun things none of us have ever lost,” Lazar said. “So if we ring that bell in you, well … we’re toys.”

The show goes from 9 p.m. to 2 a.m. Thursday at T.T. the Bear’s Place, 10 Brookline St., Central Square, Cambridge. Attendees are encouraged to dress theme-appropriately. For information, click here.