GuitarBot couldn't keep a tune. "It's too high at the top, and too low at the bottom," Michael Hearst complained as he hopped onto the platform, giving the tuning knob a hopeful quarter-turn. But when he climbed down again and hit a button on his keyboard, the mechanical bridge slid back up the track, thumbing a note before wailing off-pitch once again.

Faced with this minor malfunction, Hearst was going to have to make do with GuitarBot's other three strings if he wanted to finish recording the "The Saddleback Caterpillar," a new song for his upcoming album, Songs for Unusual Creatures. Hearst has sought unusual inspiration in the past, but it's his recording methods that have long been the most unorthodox.

The 36-year-old musician revels in the oddities of the musical world. He played a theremin in Carnegie Hall, and founded his band One Ring Zero around the claviola, an accordionlike wind instrument which was produced for only a few months in the 1990s.

Last fall, Hearst was riding his bike down a street in Brooklyn when he noticed a mysterious storefront next to an Italian bistro. As he peered inside the grime-covered window at a bunch of mechanized musicians, engineer and musician Eric Singer struck up a conversation. Singer explained that GuitarBot, along with the xylophonelike Ill-Tempered Clangier and two dozen percussion-based ModBots, are part of the League of Electronic Mechanical Urban Robots, or LEMUR project in New York City.

Singer founded LEMUR in 2000 to create novel musical instruments that integrate robotic technology. "LEMUR's philosophy is to build robots that are new types of musical instruments," the project Web site says, "as opposed to animatronic robots that play existing instruments." Singer first described GuitarBot at the 2003 conference on New Interfaces for Musical Expression in Montreal, and has been developing a growing ensemble ever since.

Hearst was hooked that afternoon, and a day later he sent in a proposal to spend the next several months recording an entire album with the help of the LemurBots. On a recent weekday inside the Lemur studio, Hearst pulls up the computer file for his song "The Bilby," named after an Australian marsupial mouse. "It's a night-dweller," he says, "I wanted to have something ominous, a night sound, and to have a hopping sound come in." The bots come on, one by one: the arpeggios on the Clangier, the plucking of the GuitarBot joined by humans on the claviola and tuba, and soon the room fills with the sound of the clanging, rattling and whirring of the ModBots.

What's the chance the LemurBots will put his band out of the job? "It would be really boring music if it was just robots," he says. At his last show, he adds, "I made a joke to the tuba player that he was going to be out of the job soon...and the computer crashed. I was trying to reboot, and the tuba player said, 'I don't know about the robots, but the humans are ready to go.'"

Hearst and his four-piece band will be playing their next robot-enhanced gig at Joe's Pub in New York City on September 17.