Procedural Sound Design/Audio

Procedural audio describes audio that is created using a procedure or algorithm. This definition is of little use in game audio because it would include that is not created or manipulated in real time. Farnell includes algorithmic composition as a type of procedural audio and according to Curtis Roads, W.A. Mozart's Musikalisches Wurfelspiel could be described as a method of algorithmic composition (Roads, 1996), but this method provides no potential for interactivity during playback. Procedural audio has been further described as audio that is "...created in real-time according to a set of programmatic rules and live input."(Farnell, 2007) This description is more useful as it now allows purely for audio that is manipulable and interactive during playback as is found in game audio. The paper by Farnell suggests that the term procedural audio can be used to describe a number of different types of audio: Non-Linear sound Sequenced sound Synthetic sound Generative sound Stochastic sound Algorithmic sound AI sound

If any of these descriptors can be applied to the sound or music then it is 'procedural'. It should be noted that because a more general definition for the term 'procedural audio' does exist then one can expect that any use of that term may be referring to audio that is not necessarily manipulable in real time in the way that Farnell describes.

A distinction is drawn between procedural audio and procedural sound design in the book 'Game Audio Implementation'. Here, procedural sound design is said to be "manipulating pre-existing assets," whereas procedural audio is, "a term more frequently used when systems of synthesis are used to generate the sounds themselves..."(Stevens, Raybould, 2016) A similar distinction is drawn between 'transformational' and 'generative' algorithms in creating music (Wooller, 2005). Transformational algorithms for music do "...not have a significant impact on the general musical predisposition of the data representations or the actual size of the data, but can alter the information." Generative algorithms for procedural music are defined as "...being generative when the resulting data representation has more general musical predisposition than the input and the actual size of the data is increased." Roads uses similar terminology when he refers to a type of compositional algorithm as being a language, "...for generation and transformation of musical data and control of musical processes." These definitions of 'transformative' and 'generative' algorithms are similar to the differences between procedural sound design and audio described by Stevens and Raybould. All of these styles of algorithmic music fit the first definition given by Farnell of procedural audio.

It seems that 'procedural audio' is an umbrella term that can describe any music or sound that is either manipulated in real time or not.

The 'transformative' algorithms for music are a type of procedural sound design. Procedural sound design describes the same transformative method but is not necessarily applied to music.

Collins (2009) suggests that transformative music algorithms are very commonly found in games whereas generative algorithms are rarely used but have potential to become increasingly popular.

Wooler actually suggests a third type of procedural algorithm known as an analytic algorithm. This type of algorithm would, "...reduce the potential data size and the general musical predisposition of the representation by extracting specific features." Providing more data than is needed to create the sound is wasteful in terms of memory and provides no more functionality than good generative algorithms. Analytic algorithms therefore have little potential in game audio.

Stevens, R. and Raybould D. (2016). Game Audio Implementation, CRC Press, p. 59

Roads, C (1996). The Computer Music Tutorial, MIT Press, pp 821 - 825

Collins, K. (2009). An Introduction to Procedural Music in Video Games. Contemporary Music Review, 28(1), pp. 5 - 15

Farnell, A (2007). An Introduction to Procedural Audio and its Application in Computer Games. [online]. Available at: http://cs.au.dk/~dsound/DigitalAudio.dir/Papers/proceduralAudio.pdf [Accessed 10/10/2016].

Wooller, R., Brown, A., Miranda, E., Berry, R., Diederich, J. (2005). A framework for comparison of process in algorithmic music systems. Generative arts practice (pp. 109–124).