Ben Johnston, a prolific and influential composer who used microtonal tuning systems to create a large and varied catalog of chamber works, stage pieces and music for orchestra, choir, voice and solo piano, died on Sunday in Deerfield, Wis., near Madison. He was 93.

Michael Mitchell, his son-in-law and personal assistant, said the cause was complications of Parkinson’s disease.

Mr. Johnston was an unusual avant-gardist: His music was so melodically engaging, rhythmically vital and structurally transparent that listeners who were unaware of his tuning experiments and their complex theoretical underpinnings heard his works as essentially neo-Romantic.

In addition to using microtonality — a system in which the octave is often divided into dozens of pitches rather than the traditional 12 — Mr. Johnston sometimes used serial techniques, in which pitches were presented in a predetermined sequence. He invented his own notation systems to account for his tunings, which could change from piece to piece.