are changeable. This means that each point of discontinuity is a target for a compositional action (Schilingi 1998). Because this class inherits the properties of the Sample class, each one of the Sample properties described in the previous section is also modifiable inside a Figure. Its edit window (Figure 3) comprises several tools allowing a quick assignment of new values for phase shift, speed variation and filtering to the entire figure. Among them we can find two resizable multislider panels for speed variation and phase shift edit, a breakpoint filter editor to filter evolution within the Figure, several reordering, scaling and reverse tools that can affect the whole figure or just one of its attributes. 3.3 Meso-structure Meso-structure is the locus for polyphonic development of more complex Figures (Figure 4). Just like the interdependency that has been established between Samples and Figures, a Meso-structure can encapsulate several Figures. Its editing window comprises an eight-layer sequencer where individual onsets can be assigned to each contained Figure. All objects inside a Meso-structure keep their individual methods and properties. A Figure remains a Figure and can therefore be modified through its own editor which, in turn, gives access to the Sample editor. In fact, the three main IRIN editors (Sample editor, Figure editor and Meso-structure editor) are permanently linked. The way IRIN's interface was built directly reflects all class dependencies shown in figure 1. Figure 4: Meso Structure Editor window. Figure 3: Figure Editor window. A granulator is also available inside the Figure Editor. It can be used to output a stream of a pre-defined number of particles with a particular behaviour as regards the evolution of their properties. The evolution of the duration of its Samples, of the distance between them, of their phase shift and of their filtering can be set before outputting into a Figure object. Despite the use of the global laws strategy, the Figure obtained can be then locally changed "by hand" since each one of its elements is an instantiation of the Sample object that, as previously mentioned, can be modified in several ways. Direct manipulation, therefore, plays an essential role in this context, since morphological properties of a given Figure (gestalt) arise from its local singularities (Vaggione 1996; Vaggione 2002a). Eventually, after all local changes have been performed, a Figure results as a configuration (or pattern) so unified as a whole that it cannot be described merely as a sum of its parts. How to achieve this is already a compositional issue. 4 Timeline At the top-level we have the Timeline window. Timeline is basically a 4 track sequencer were Samples are represented as a coloured bar, their size reflecting their duration (Figure 5). Figures are displayed as a white rectangle labelled with the respective figure library name. The notion of track used is somehow different from the one we often find in traditional audio multi-track sequencers. For instance, whether in ProTools or in Digital performer, panning and volume curves are edited in the track affecting the sound blocks placed in background. In the case of IRIN's timeline, because each sound object keeps track of its internal data, their properties (including panning and envelope amplitude) are a track-independent feature. Thus, every event always keeps the exactly same properties if moved back and Proceedings ICMC 2004
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