Pattern definition is a fundamental component of music composition. Musical patterns may exist at any level of a composition, from transitory surface phenomena to deep structural organization. A pattern may be defined for a single sound attribute such as frequency, or it may relate multiple sound attributes (such as frequency, rhythm and amplitude) in parallel. This paper describes the implementation of item streams, an object-oriented representation of musical patterns that is capable of controlling any number of sound attributes simultaneously. The facility predefines a number of ready-to-use pattern types, from simple sorts of serial orderings to more complex random selection and networking strategies. Because of its object-oriented design, item streams are easily extended to include new patterns, functionality and relationships between sound variables. As a rule, all patterns permit each element of data or pattern control information to be a basic value or another pattern. Hybrid patterns are then created from the basic pattern set through recursive definition, by expressing a larger pattern in terms of one or more subpatterns. There is no limit to the depth of pattern definition. The scope of each subpattern is controlled by its period length, which sets the current limit of a subpattern’s contribution to its superior pattern. The period length may also be used to force breadth first or depth first traversal, or it may vary dynamically according to its own pattern.
ASJC Scopus subject areas
- Visual Arts and Performing Arts