Harry Partch

Harry Partch (June 24, 1901 – September 3, 1974) was an American composer and instrument builder. He was one of the first twentieth-century composers to work extensively and systematically with microtonal scales, writing much of his music for custom-made instruments he built himself, tuned in 11-limit just intonation.

http://en.wikipedia.org/wiki/Harry_Partch