Andrew Bird takes off

Everything in Andrew Bird's song ''Masterfade" -- from the sky to soybeans -- is made of digits. The green grass is 6. June bugs are 8. At first the assignments seem arbitrary. Several spins later, the edges of perception softened by reverb-heavy whistling, it all adds up.

Not coincidentally, the numbers with which the artist measures his own life are swelling. Here's a recent accounting: three -- the number of times Bird made and remade his new album ''The Mysterious Production of Eggs"; 28 -- the number of shows he's played in the past 32 days; 30 or 40 or 50 -- different versions Bird has performed of each of his songs. It's hard to keep track. He rewrites them every night.

Bird is bone-tired. His voice trembles over the phone from his home in Chicago, where he's returned for four days before hitting the road again for God knows how long on a tour that stops at the Middle East on Tuesday. He sounds desperate for soup and a nap. If Bird weren't the person who more or less single-handedly made one of the most sonically sublime, linguistically bewitching pop albums in memory, guilt over keeping him vertical and verbalizing would have cut short the conversation before it stretched -- like everything else -- to preposterous proportions.

''I put a lot of pressure on myself," he says. ''My nerves are going. I think I've definitely crossed the line."

One senses that crossing the line is Bird's status quo. While peers tread the landscape of heartache and romance, Bird writes riddled verse about the laws of physics and the mysteries of childhood. He ran out of the usual musical reference points -- favorite records, familiar chord changes -- two years ago, he says, around the same time he began whistling in earnest. Bird, a conservatory-trained violinist whose world-class whistle is all over the new album, speaks at length about his tongue's unique attributes. It is, according to the artist, a secret weapon.

There are others -- most significantly Bird's aspiration to carve out an original niche in pop, the most derivative of musical genres.

''I feel like I'm on an opposite trajectory from a lot of people, who start in punk and are self-taught and find more sophisticated music later," says Bird, who followed his prodigal youth as a concert violinist with albums that plumbed Weimar-era cabaret, New Orleans jazz, early blues, Irish and gypsy music, and nouveau swing as an auxiliary member of the Squirrel Nut Zippers. ''I didn't listen to pop music in high school when you're supposed to. I hated the Cure. I was on this linear path, getting more and more complicated and trying to learn everything, and I found that to be finite. Now I find it endlessly challenging to try to write a good song, a really simple song with a melody. That's what keeps me at it."

Bird wouldn't like it, but it's worth pointing out a few relevant associations, among them the artist's Beatles-esque mastery of melody, a slurred croon reminiscent of Radiohead's Thom Yorke, a taste for decadence that he shares with Jeff Buckley and Rufus Wainwright, and the sort of elegantly skewed, Magnetic Fields-caliber wit that produces such improbable rhymes as ''Disney bride" and ''formaldehyde."

''I'm not the kind of writer who fills books with words and poetry and fits it into music," Bird says. ''Words come like melodies: Something catches in my mind for no reason and I become obsessed. Oftentimes on this album there's a character who's trying to figure something out, a scientist, someone who's trying to measure and quantify but isn't having much luck, and we're rooting for him to fail at making things formulaic. There's also a theme of apocalypse. But I envision a nice apocalypse, the old '80s-style 'Mad Max' variety where everyone is having a great time in burned-out buildings and, even though the economic infrastructure has collapsed, there's plenty of snacks. The [bull] has fallen away and everyone is talking to each other. I guess it's longing for community."

Bird has recently returned to Chicago after five years of self-imposed isolation on a farm in northern Illinois. That's where he made his first attempt at recording ''The Mysterious Production of Eggs" with a full band in the studio that he built in a barn. The songs, he says, were packed with excitement and intensity, but the barren landscape was changing the way Bird heard music. He shelved the album and made a mini LP, 2003's ''Weather Systems," a collection of lush, dynamic soundscapes. A second effort, recorded in Nashville, erred on the side of ambient.

''It sounded like these big clouds of gas sitting on this tiny rhythm section," says Bird, who had by that point drained his bank account. ''What finally pulled it together was an endorsement, I guess, from this producer who's sort of a patron, and if he likes you he'll invite you out to his studio in LA."

Bird's patron was Tony Berg, a veteran producer (X, Public Image Ltd., Aimee Mann) and former A&R executive at Geffen and Virgin.

''I was struck by his musicality and thoroughly original point of view and simply said, 'How can I be helpful?' " Berg recalls. ''Andrew is among America's truly great songwriters, but he's a funny guy, a very gentle and private guy, and surprisingly reticent. I think that being at my home, having dinner every night with this loud, engaged family was comforting for him."

Indeed, Bird -- who plays most of the instruments on ''The Mysterious Production of Eggs," released in February on Ani DiFranco's Righteous Babe label -- knocked out the third and final version of the record in a week and a half. He and his touring mate, Martin Dosh, each armed with loop pedals and samplers, rebuild the songs each night: Bird on violin, glockenspiel, guitar, whistling, and voice, Dosh on drums and electric piano. It's an exhausting, exhilarating ritual.

''Performing and writing have become the same thing, the same process," Bird says. ''I've let go of the idea of trying to re-create the record. All you need onstage is the excuse to do something musical."

Andrew Bird plays the Iron Horse in Northampton Monday and the Middle East

Downstairs on Tuesday. Tickets for the Cambridge show are $13 in advance, $15 at the door, available at the Middle East box office. Visit www.ticketmaster.com or call 617-931-2000.

Joan Anderman can be reached at anderman@globe.com.