This fall, New York indie-rock outfit the Fiery Furnaces will release a mammoth live album of material recorded at concerts from the end of 2005 through this February. It’s yet another curveball from the brother-and-sister duo of Matthew and Eleanor Friedberger. Since making their debut in 2003 with the relatively stripped-down “Gallowsbird’s Bark,” the Friedbergers have shape-shifted through various pop and rock styles during the course of their brief yet prolific career. The only thing that hasn’t changed is their antic energy and intelligent wit.

“A friend of mine who works in magazines said, ‘This is what the record industry needs right now, a breakthrough crossover release,'” the duo’s primary songwriter and multi-instrumentalist, Mr. Friedberger, said about their triple-LP live album. Speaking by phone from Wooster, Ohio, where the Fiery Furnaces were beginning a week-long, five-date mini tour that will lead them to Brooklyn’s Southpaw on Saturday, Mr. Friedberger proceeded to clarify that he was absolutely, positively joking. “We’re just enough of a famous band for people to know that a three-LP live record by the Fiery Furnaces wouldn’t necessarily be the record that is going to reinvigorate the music industry.”

Candid, chatty, and refreshingly deadpan funny at 10 a.m., Mr. Friedberger, 35, was strolling around the north-central Ohio college town. He made frequent references to the names he came across on storefronts and street signs to illustrate his points, and even reported that he had picked up some Wayne County real estate guides, from whose pages he hoped to cull some ideas. He and his sister are well versed in finding inspiration in all corners. At their “Democ-Rock Live” shows this past January and February, the band asked people — as it will this weekend in Brooklyn — to write requests and/or word ideas onto pieces of paper and pass them to the stage for possible use.

“I’m sure there’s lots of material that needs to be in rock lyrics in those real estate listings,” Mr. Friedberger said, without a hint of sarcasm in his voice. “It’s easier to write lyrics on tour. Well, that’s not necessarily true, because you don’t have everything you have at home. So you have to write stuff all the time, otherwise when you need to write something it’ll be weird and you’ll feel pressured. So if you just write the whole time, then it’s like doing any job — you have to imagine you like it, otherwise you hate it.”

From the melodic throb and wordy counterpoints of “Leaky Tunnel” (from “Gallowsbird’s Bark”) to the complex, mixed meters of “Right by Conquest” (from last year’s expansive “Widow City”), the Fiery Furnaces’ songs are little marvels of words and music bouncing into and off each other to create rippling interplays. It’s a cliché to talk about a singer’s voice as an another instrument in a song’s mix, but only rappers really exploit the physical sound of forming and uttering their lyrics as rhythmic devices. More often than not, a rock singer’s words roll along with a song’s backing meter.

Rarely is that the case with the Fiery Furnaces’ song lyrics.

“Rock music should have words that are rock ‘n’ rolly,” Mr. Friedberger said. “A little vulgar, a little bit friendly — that’s what’s great about rock music. So you want to do that, especially with them being sort of noisy words, words that are awkward to say.”

He cited “Pricked in the Heart,” from “Widow City,” as an example in which his sister crams the song’s 300-plus words into a little more than two minutes of jaunty, folky, sparse music. “I wanted to have as simple a musical structure as possible and then have the rhythm of the words be apparently ill-fit for how much space there is for those syllables,” Mr. Friedberger said of the song. “So the phrasing of the words is contrary to that of the music; it doesn’t fit at all. Another song, ‘Right by Conquest,’ also has very, very long lines that you wouldn’t fit into a normal rock song.”

“Stuff like that” is what he likes to do, he continued. “It’s basically legitimate to write songs whose whole purpose is to get people to sing along to them — and then that’s when you want it to be some weird phrase, like ‘Allbrite Radiator, Allbrite Radiator’ — I’m standing by a shop called Allbrite Radiator. And if you say it over and over, then people might want to sing along to it.”

The Fiery Furnaces’ busy songs often traipse widely, as they do in the whimsical “My Egyptian Grammar,” from a half-Samoan girl and the Oriental Institute to a French canal boat. Whether a word works or doesn’t is often discovered during an album’s genesis.

“The way the band works for the two of us is we make a plan, then I go away and write it,” Mr. Friedberger said. “And usually, it is according to plan, but sometimes I have to convince Eleanor. She always asks, ‘How is this going to fit?’ But that’s what writing a song is — seeing how it’s supposed to work and finding out how it’s supposed to work, usually by it not working.”

The most recent conclave came during the Fiery Furnaces’ most recent tour, earlier this year, when the band voted on what the next record should be. Given Mr. Friedberger’s whimsical nature and daft sense of humor, it might be best to take his account of the result with a grain of salt.

“There were eight choices and one was a funk record,” he said. “That was one choice, a lot of them were close, but that was what clearly won. So I guess that’s what we’ll make — a funk record.”