Extension is a three-sectional, one-movement composition for orchestra exploring various permutations of a single motivic unit. The central priority has been to present this motive in a variety of textural situations with a harmonic accompaniment evolving from a macrotonal to a microtonal setting. Some of the devices utilized to realize this priority are mixed-instrument timbral combinations, tone clusters, multiphonics for brass and woodwinds, multiple stops for strings, and superimpositions of multiphonics. Extension is unique in two areas. First, the evolutionary progression from a macrotonal to microtonal harmonic texture is made possible by expanding the priorities of instrumental performing. Second, the use of multiphonics for full orchestra is unique to this work.