Generative music is a term popularized by Brian Eno to describe music that is ever-different and changing, and that is created by a system.
There are four primary perspectives on "Generative Music" (Wooller, R. et al., 2005) (reproduced with permission):
Music composed from analytic theories that are so explicit as to be able to generate structurally coherent material (Loy and Abbott 1985; Cope 1991). This perspective has its roots in the generative grammars of language (Chomsky 1956) and music (Lerdahl and Jackendoff 1983), which generate material with a recursive tree structure.
Music generated by a system component that ostensibly has no inputs. That is, "not transformational" (Rowe 1991; Lippe 1997:34; Winkler 1998). The Koan software by SSEYO – used by Brian Eno to create Generative Music 1 – is an example of this.
Non-deterministic music (Biles 2002), or music that cannot be repeated, for example, ordinary wind chimes (Dorin 2001). This perspective comes from the broader generative art movement. This revolves around the idea that music, or sounds may be "generated" by a musician "farming" parameters within an ecology, such that the ecology will perpetually produce different variation based on the parameters and algorithms used. An example of this technique is Joseph Nechvatal's Viral symphOny: a collaborative electronic noise music symphony created between the years 2006 and 2008 using custom artificial life C++ software based on a viral model.
Many software programs have been written to create generative music, including:
- SSEYO Koan Pro (1994–2007), used by Brian Eno to create his hybrid album Generative Music 1. The SSEYO Koan software was created by Pete Cole and Tim Cole of Intermorphic, who re-acquired the Koan technology in 2008. The software was displayed in the London Science Museum's Oramics exhibition (2011-2012) 
- Intermorphic's Noatikl (2007–present). Noatikl is described by Intermorphic as "The Evolution of Koan", and was launched in 2007 as a replacement for the no-longer-available Koan. Noatikl is a Generative Music engine that generates MIDI events in accordance with a rule set that can be manipulated in real-time through a graphical user interface. Noatikl can optionally operate as a Hyperinstrument by responding to incoming MIDI event data, with optional extension through user-supplied Lua scripts. Noatikl is available as a standalone tool for both Mac OS X and Windows, and there are VST and AU plug-ins for desktop music sequencers. Noatikl 2 was released in May 2012.
- Intermorphic's Mixtikl (2004–present), a portable generative music lab and loop mixing system with variants for the iPhone, iPod, iPad, Mac OS X and Microsoft Windows, as well as a web browser plug-in, and VST and Audio Unit plug-ins for desktop music sequencers. Mixtikl includes an embedded Noatikl generative music engine and Noatikl editor, and the Partikl modular synthesizer system.
- IMPROVISOR for AudioCubes IMPROVISOR for Audiocubes, used by Mark Mosher and other electronic music composers. IMPROVISOR and Audiocubes were created by Bert Schiettecatte of Percussa.
- FractMus, developed by Gustavo Díaz-Jerez is a real-time algorithmic music generator.
-  a new format for recorded music that reinterprets the piece on each listening. created by Gwilym Gold and Lexx and released on [Mac OS X] [Mac iOS]
- Tune Smithy, developed by Robert Walker, for Windows generates music real time using a musical construction similar to the Koch snowflake fractal.
- Nodal (2007–present), a graph-based generative composition system for real-time MIDI sequence generation (for Mac OS X and Windows)
- Bubble Harp developed 1997-2011 by Scott Snibbe for the iPad, iPhone, and iPod Touch.
- Bloom developed 2008 by Peter Chilvers together with Brian Eno for the iPhone and iPod Touch.
- Karlheinz Essl's sound environments fLOW (1998–2004) and SEELEWASCHEN (2004)
- Metascore (Sorensen, Brown and Hedemann 2008) supports the generative composition of music to video timing cues.
- MusiGenesis (2005), a program that for Windows that evolved music.
- Lauri Gröhn has developed Synestesia software that generates music (midi file) from any photos in a few seconds.
- Many algorithmic music projects are also considered to be generative (see algorithmic.net for some of them).
- Modern generative music games such as Rez have been considered generative in character.
- Sergio Maltagliati generative music software .
- Kepler's Orrery, an interactive gravity simulator that generates music, developed in 2007 as an open-source Java project and ported to the iPhone in 2009.
- Dub Cadet, is the generative arduino based software and hardware interface for creating music through rotational motion developed by Noah Hornberger in 2012.
'Scape' (software) app developed by BRian Eno and Peter Chilvers for the iPod 2012
Other Notes 
- Brian Eno, who coined the term generative music, has used generative techniques on many of his works, starting with Discreet Music (1975) up to and including (according to Sound on Sound Oct 2005) Another Day on Earth. His works, lectures, and interviews on the subject have done much to promote generative music in the avant-garde music community. Eno used SSEYO's Koan generative music system (created by Pete Cole and Tim Cole of Intermorphic), to create his hybrid album Generative Music 1 (published by SSEYO and Opal Arts in April 1996), which is probably his first public use of the term "Generative Music".
- Lerdahl and Jackendoff's publication described a generative grammar for homophonic tonal music, based partially on a Schenkerian model. While originally intended for analysis, significant research into automation of this process in software is being carried out by Keiji Hirata and others.
- In It's Gonna Rain, an early work by contemporary composer Steve Reich, overlapping tape loops of the spoken phrase "it's gonna rain" are played at slightly different speeds, generating different patterns through phasing.
- A limited form of generative music was attempted successfully by members of the UK electronic music act Unit Delta Plus; Delia Derbyshire, Brian Hodgson and Peter Zinovieff, in 1968. However, its use would only be popularized later on.
See also 
- Generative art
- Algorithmic composition
- Cellular automaton
- Change ringing
- Computer-generated music
- Interactive music
- Live coding
- Musikalisches Würfelspiel
- Observatori 2008: After The Future, p. 80
- Joseph Nechvatal Interview: see end for mention of viral symphOny
- Artscape - Brian Eno In Conversation 2009(video)
- Artística de Valencia, After The Net, 5 – 29 June 2008, Valencia, Spain: catalogue: Observatori 2008: After The Future, p. 80
- Biles, A. 2002a. GenJam in Transition: from Genetic Jammer to Generative Jammer. In International Conference on Generative Art, Milan, Italy.
- Chomsky, N. 1956. Three models for the description of language. IRE Transcripts on Information Theory, 2: 113-124.
- Collins, N. 2008. The analysis of generative music programs. Organised Sound, 13(3): 237–248.
- Cope, D. 1991. Computers and musical style. Madison, Wis.: A-R Editions.
- Dorin, A. 2001. Generative processes and the electronic arts. Organised Sound, 6 (1): 47-53.
- Eno, B. 1996. Generative Music. http://www.inmotionmagazine.com/eno1.html (accessed 26 February 2009).
- Essl, K. 2002. Generative Music. http://www.essl.at/bibliogr/generative-music.html (accessed 22 Mar 2010).
- García, A. et al. 2010. Music Composition Based on Linguistic Approach. 9th Mexican International Conference on Artificial Intelligence, MICAI 2010, Pachuca, Mexico. pp. 117-128.
- Intermorphic Limited History of Noatikl, Koan and SSEYO (accessed 26 February 2009).
- Lerdahl, F. and R. Jackendoff. 1982. A generative theory of tonal music. Cambridge, Mass: MIT Press.
- Lippe, C. 1997. Music for piano and computer: A description. Information Processing Society of Japa SIG Notes, 97 (122): 33-38.
- Loy, G. and C. Abbott. 1985. Programming languages for computer music synthesis, performance and composition. ACM Computing Surveys, 17 (2): 235-265.
- Rowe, R. 1991. Machine Learning and Composing: Making Sense of Music with Cooperating Real-Time Agents. Thesis from Media Lab. Mass.: MIT.
- Viral symphOny is downloadable for free at www.archive.org
- Winkler, T. 1998. Composing Interactive Music. Cambridge, Massachusetts: MIT Press.
- Wooller, R., Brown, A. R, et al. A framework for comparing algorithmic music systems. In: Symposium on Generative Arts Practice (GAP). 2005. University of Technology Sydney.