- Paul Griffiths
A term applied to music whose composition and/or performance is, to a greater or lesser extent, undetermined by the composer.
As defined above, the term ‘aleatory’ (‘aleatoric’ is an etymological distortion) applies to all music: it is impossible for a composer to prescribe every aspect in the realization of a composition; even the sound result of a tape playback will depend on the equipment used and the acoustic conditions. However, the term is usually restricted to music in which the composer has made a deliberate withdrawal of control, excluding certain established usages which fall within this category: for example, keyboard improvisation, the cadenza, the ossia, the ad libitum, unmeasured pauses, alternative scorings and the provision of sets of potentially independent pieces (e.g. the Goldberg Variations). Three types of aleatory technique may be distinguished, although a given composition may exhibit more than one of them, separately or in combination: (i) the use of random procedures in the generation of fixed compositions (...