Don’t look for conventional signs of music making in the West Oakland workshop of Paul Dresher, a composer. The piano has been covered to protect it from dust. A broken drum set sits in a corner. But if you are interested in hearing a tune on the “Hurdy Grande,” a 10-foot-long wooden sound box and aluminum frame with a motor-driven wheel for bowing the instrument’s seven strings, you have come to the right place.When Mr. Dresher — a composer whose output straddles commissions from the San Francisco Symphony and experimental works for musical theater and film — plucks or presses the contraption, he brings forth assorted sounds reminiscent of a sitar and a guitar played with a whammy bar.Mr. Dresher is among a loose group of musicians based in the Bay Area who are working to create new musical devices. Building on the legacy that was started by 20th-century West Coast inventor-composers like Harry Partch and Lou Harrison, these musicians are paying special attention to the terrain between the world of computers and traditional acoustic musical instruments to expand musical frontiers.