This tutorial demonstrates basic Texture creation, configuration, and deployment in musical structures. This chapter is essential for using athenaCL for algorithmic music production.
A TextureInstance (or a Texture or TI) is an algorithmic music layer. Like a track or a part, a Texture represents a single musical line somewhat analogous to the role of a single instrument in an ensemble. The music of a Texture need not be a single monophonic line: it may consist of chords and melody, multiple independent lines, or any combination or mixture. The general generative shape and potential of a Texture is defined by the TextureModule. A Texture is an instance of a TextureModule: a single TextureModule type can be used to create many independent instances of that type; each of these instances can be customized and edited independently. Collections of TextureInstances are used to create an EventList, or the musical output of all Textures.
A TextureInstance consists of many configurable slots, or attributes. These attributes allow the user to customize each Texture. Attributes include such properties as timbre (instrument and parametric timbre specifications), rhythm (duration and tempo), frequency materials (Path, transposition, and octave position), and mixing (amplitude and panning). Other attributes may control particular features of the Texture, like the number of voices, position of chords, or formal properties.
Most attributes of a TextureInstance are not fixed values. Unlike a track or a part, a Texture often does not have a fixed sequence of values for attributes like amplitude, or even fixed note-sequences. Rather, attributes of a Texture are algorithmic objects, or ParameterObjects. Rather than enter a value for amplitude, the user chooses a ParameterObject to produce values for the desired attribute, and enters settings to specialize the ParameterObject's behavior. Rather than enter note-sequences, the Texture selects and combines pitches from a Path, or a user-supplied sequence of pitch groups. In this way each attribute of a Texture can be given a range of motion and a degree of indeterminacy within user-composed boundaries.
A TextureInstance is not a fixed entity: it is a collection of instructions on how to create events for a certain duration. Every time an EventList is created, each Texture is "performed," or called into motion to produce events. Depending on the TextureModule and the Texture's configuration, the events produced may be different each time the EventList is created.
athenaCL is designed to allow users work with broad outlines of musical parameters and materials, and from this higher level organize and control combinations of Textures. This should not be confused with a much higher level of algorithmic composition, where an algorithm is responsible for creating an entire composition: its style, form, parts, and surface. athenaCL is unlikely to produce such "complete" musical structures. Rather, athenaCL is designed to produce complex, detailed, and diverse musical structures and surfaces. Combinations of parts and construction of form are left to the user, and can be composed either in athenaCL or in a Digital Audio Workstation where athenaCL EventOutput formats, such as MIDI files or Csound-rendered audio files, can be mixed, processed, and combined in whatever desired fashion. Alternatively, MIDI files produced with athenaCL can be modified or combined in traditional sequencers and notation editors.