Two composers, who are known for using little number of notes.

Scelsi sounds symphonic, single note is played by multiple instruments, varying in dynamics.

Feldman sounds more dissonant, chamber long non-changing chords. (Feldman, Scelsi)

A very interesting yet simple island showing different approaches to making a long composition out of a single texture or pitch. Both composers are microtonal. Yet Scelsi works mainly for orchestra and Riley uses synths, tape loops, indian music and non-orchestra instruments. (Scelsi, Riley)