In music a cloud is a sound mass consisting of statistical clouds of microsounds and characterized first by the set of elements used in the texture, secondly density, including rhythmic and pitch density [Need quotation to verify]. Clouds may include ambiguity of rhythmic foreground and background or rhythmic hierarchy.
- Iannis Xenakis's Concret PH (1958), Bohor I (1962), Persepolis (1971), and many of his pieces for traditional instruments 
- György Ligeti's Clocks and Clouds (1972-3)
- La Monte Young's The Well Tuned Piano
- Bernard Parmegiani's De natura sonorum (1975) 
Clouds are created and used often in granular synthesis. Musical clouds exist on the "meso" or formal time scale. Clouds allow for the interpentration of sound masses first described by Edgard Varèse including smooth mutation (through crossfade), disintegration, and coalescence. 
Curtis Roads  suggests a taxonomy of cloud morphology based on atmospheric clouds: cumulus, stratocumulus, stratus, nimbostratus, and cirrus; as well as nebulae: dark or glowing, amorphus or ring-shaped, and constantly evolving.
- Roads, Curtis (2001). Microsound. Cambridge: MIT Press. ISBN 0-262-18215-7.
- Atomic Cloud Atomic Cloud is an easy to use real-time grain cloud generator for Windows
This music theory article is a stub. You can help Wikipedia by expanding it.