The composer Gyorgy Ligeti has developed the use of micro-polyphony. in which shifting masses of densely detailed "clouds" of sound are very slowly transformed over time. This idea of basic forms staying the same while individual shapes evolve can be explored with tuned instruments. Choose some notes from any type of scale (chromatic, pentatonic, and so on) to make a cluster. While some players maintain this as a drone, other players, using instruments that can play microtones - string and wind instruments, electronic keyboards, and voices - gradually bring a chosen note in and out of focus until they move to a different note. This languid near-melody momentarily redefines the sound into a new static shape, then the same process happens again. If players genuinely make their changes at random, the effect is hazy and magical. Listen to Ligeti pieces such as Apparitions (1958-9), Atmospheres (1961, used in the film 2001: A Space Odyssey) and Clocks and Clouds (1973).