For members of Fishtank Ensemble, the music world is their oyster.

The cover of Fishtank Ensemble's latest CD, "Woman in Sin," looks like a pop-up greeting card with the eclectic music group's images in front of, or perhaps in, an aquarium surrounded by denizens of the deep.

Fishtank Ensemble, which played Musikfest in 2011, plays at 8:30 p.m. Sept. 27, Mauch Chunk Opera House, Jim Thorpe.

The group is: lead singer Ursula Knudson (depicted as a mermaid on the CD cover), violin, banjolele, theremin, percussion, saw; Fabrice Martinez (married to Knudson), violin, violintromba; Douglas Smolens (aka El Douje), flamenco guitar; and Djordje (George) Stijepovic, double bass.

Knudson traces her mother's ancestry to Jamestown, Va., and her father is Norwegian. She met European-born Martinez in Venice, Italy. Smolens is a Guadulara, Mexico, native. Stijepovic is from Serbia.

In a recent phone interview from Lancaster County where band members were visiting after a Wilmington, Del., gig, on a tour that includes Baltimore, Chicago, and Portland, Me., Knudon and Smolens said Fishtank Ensemble's diversity serves the group's songs and performances.

"That's pretty much why we are a band in the first place. When we played together, it was very natural the different styles mixed together, without really thinking about it," Smolens says.

"Everybody brings some songs that we already know. Fabrice, the violinist, tries to bring the most. We want to find a song that we can kind of add something to. Even though you'll find a diversity in the styles, there's a unifying factor: our creative approach to it," says Smolens.

Smolens credits Stijepovic with taking Fishtank Ensemble to new depths of sound.

"We went through about eight bass players. Finally, we found him [Stijepovic]. He plays bass and drums. The slap bass creates a percussion effect," he says.

"The music we're playing is very challenging. That's the goal that just the fun comes through and not that work that went into it," says Smolens.

Classically-trained Knudson has a three and one-half octave vocal range. "When we get a new song, a lot of times it doesn't work. And then it finally works. Like, each song has its own character, and then I find it," she says.

The group sings in English, French, Spanish and Serbian.

The willowy high-pitched saw emulates Knudson's voice.

"Playing the saw is very much like singing. Because I'm a high soprano, I'm not trying to make it sound like that. But who knows? Because I play it [the saw] so much, maybe I adapted.

"My voice darkened when I had my son, " she adds. Her and Martinez's son, Ezra, is six.

Fishtank Ensemble is regarded as part of the New Vaudeville Movement, which includes modern takes on old-timey music, hot jazz, burlesque, fire-dancing and sideshow.

"We're proud to be a part of it," Knudson says. "It's very good to look to the past for inspiration. If you look at old vaudeville, they would do amazing things

"It's hard to struggle as an independent group. It's very difficult. We want to have artistic integrity. It's so hard to be a musician in this country, why would you abandon your integrity and go mainstream?"