AN INSTRUMENTAL MAN.

Mark Stewart rarely leaves his apartment in Brooklyn without an instrument of his own design, usually a chaladoo. A chaladoo is a version of a chalumeau, a Baroque clarinet with finger holes instead of keys. The chaladoo has the profile of a bass clarinet, but it is made of plastic plumbing pipe and plastic plumbing fixtures, to which Stewart has attached the mouthpiece of a saxophone. Because he is often interrupted while playing the chaladoo by people who want to know what it is, he has drawn on one side of a four-by-seven-inch card a schematic diagram of the chaladoo and, on the other side, instructions for how to build one. He carries a stack of the cards, which he calls recipe cards. He began building instruments about four years ago and guesses that he has built about four hundred. He hopes someday to have recipe cards for all of them, but only the chaladoo has one now.

Stewart would be pretty easy to notice even without the chaladoo. He has a round face, a high complexion, and long red hair that falls nearly to his waist. He is forty-two. He grew up in Wisconsin, and designing instruments is a sideline for him. His day job is as a guitar player in Paul Simon's band. He has worked in the pit of several Broadway shows, and he is also a member of the Bang on a Can All-Stars, the Fred Frith Guitar Quartet, and Arnold Dreyblatt's Orchestra for Excited Strings, and, with Rob Schwimmer, he performs as the brainy, downtown cabaret act Polygraph Lounge, in which many of his instruments find a place.

Stewart builds his instruments in a tenement apartment on Rivington Street, which he calls the lab. He describes the lab as "a sonic salon."Leaning against the walls or hanging from nails are layers of wood and coils of plastic and metal tubing, along with a little bugle of a kind used at cricket matches in India. The lab has three bedrooms, connected by a footpath. Materials in the lab are piled on top of each other. Every now and then, they shift and something falls, the way things occasionally let loose in the woods. Stewart describes the lab as "scary but not dangerous."

Stewart classifies the instruments he makes as either macrosonophones or microsonophones. Macrosonophones can ...