Examples of phase changes are melting (changing from a solid to a liquid), freezing (changing from a liquid to a solid), evaporation (changing from a liquid to a gas), and condensation (changing from a gas to a liquid).
In contrast, in the plasma phase the atoms are dissociated, i.e.
These phases are of great interest to astrophysics, because these high-pressure conditions are believed to exist inside stars that have used up their nuclear fusion "fuel", such as white dwarves and neutron stars.
This technique was then extended to acoustic instruments as described in the above paragraph and later the change in phase was made immediate, rather than gradual, as in Reich's Clapping Music.
An example in popular music is "The True Wheel" on Brian Eno's Taking Tiger Mountain (By Strategy).
The playing of repeating phrases of the same tempo, but different metrical lengths (beats in the bar), as in the music of Philip Glass and others, is not phasing but may be considered as polyrhythms, especially if the ratio between lengths is irrational.