This house and studio space for two distinguished modern musicians occupies an infill lot on Potrero Hill. From the outside, it is a seamless black object of ambiguous scale, clad in black composition shingles. The interior is an open loft finished in stucco lustro, perforated steel, and zinc. At the center of the house are a skylit rotunda and a double spiral stair that allow daylight to penetrate down to a glass block entry at the street-level garage. There are two studio spaces at the back of the house, one of which is used for electronic composition and the creation of musical scores for films. The same geometry that serves the composer studio is appropriate acoustically for the other studio, a rehearsal space for the Kronos Quartet. The design combines the detailed acoustic requirements of the musicians studios with a comfortable domestic environment.