What's that under the Manhattan Bridge? A supple, improbably-timed drum rhythm kicks things off, followed shortly by the serpentine wail of a trumpet announcing the melody and summoning the dappled counterpoint of the accordion. Soon, the thrum of a tuba and luscious cry of a saxophone join in, rollicking through some down-and-dirty fun.

It's Raya Brass Band, which brings dance party mayhem everywhere it goes, from jam-packed Russian bathhouses to fog machine-drenched Southern clubs. Roaring like a subway train, blasting like a fanfare, the Brooklynite band has burst out of its purely Balkan inspirations to find a fresh, contemporary approach that keeps all the intricacy of tradition with an urban vibe and a heaping dose of irreverent madness.

This Train is Now (release: October 8, 2013), the band's third album, finds the members of Raya at their most delicate and their most uproarious, at their most skilled and spontaneous. Inspiration for their tunes can spring forth from a moment of group interplay, later to be refined into exquisite dance anthems or down and dirty grooves: "We'll have a gig in the street, say, and be waiting around for the organizers," explains composer and tuba player Don Godwin. "So we'll start messing around. Someone will have a phone and we'll record it. We'll be under a bridge or on the corner, some arbitrary spot, and an off-the-cuff idea will become the jumping off point for a whole track."

This Train is Now holds nothing back, just like Raya. The album, released as an 8-song vinyl disc with three additional digital-only tracks, kicks straight off with the infectious and hook-heavy "Locks and Latches," conceived by saxophonist Greg Squared during one such spontaneous jam session. "This Train is Now," composed by trumpeter Ben Syversen, is a delightful example of the intricate musical interplay between the complex sounds of the Balkans and the band members' unfailing musical imaginations.

"Riff Cloud" is another song that sprang from improvisations. Syversen explains that he found himself improvising the basic tune while tuba player Don Godwin was tapping out a particularly infectious groove on the tapan (a double-headed drum found in Serbia and elsewhere in the Balkans) on an echoing cobblestone street. Syversen recorded the melody to his cell phone for later reference. The band ended up working out the finishing touches for the tune the morning after an upstate wedding in a gazebo surrounded by sunglasses-wearing partiers at a semi-public rehearsal. Considering that at its core the brass band genre is a music for parties, groups, and interaction, this is a fitting creation story.