Up until recently, the Western art music tradition has privileged the composer as the best authority concerning issues of performance practice. This view was ingrained in the nineteenth century with European composers who sought complete control of their musical score. In the realm of Japanese contemporary music, the pieces do not conform to Western notions of cadence, phrasing or even harmonic structure. The performer furthermore has to make decisions which conflict with what the composer wrote. The piece MIRAGE for marimba (1971) by Yasuo Sueyoshi (b. 1937) will be discussed in the context of suitable methodologies to bring out the composer's ideas. The composer emerges as a 'mirage' blending with the performer in order to create the final work.