In 1977 he won the first of his numerous prizes, winning both the Queen Elizabeth International Music Composition with HETEROPHONY for string quartet (1975) and the Luigi Dallapiccola Composition Award with MUTAZIONI (1977). In 1980 KECAK (1979) was selected as the best work at the International Rostrum of Composers, and he won awards at the ISCM World Music Days with ODE for EKSTASIS (1981) in 1982, then in 1984, 1988 and 1990. The Otaka Prizes were awarded to him in 1988 for HETEROPHONY for two pianos and orchestra(1987), in 1992 for A RING OF LIGHTS, double concerto for violin, piano and orchestra, and in 1993 for INTO THE LIGHTS OF THE ETERNAL CHAOS. He was composer-in-residence of the Orchestra Ensemble Kanazawa (1993-94) and of the Tokyo Symphony Orchestra (1994-97).
Nishimura principally employs heterophony, a characteristic device of Asian traditional music, thereby subtly transforming the intervals, rhythm and melody of his dense multi-layered textures. Though similar to 'micropolyphony' of Ligetti, an Asian perspective informs his technique. Some works are heterophonic melodically, such as HETEROPHONY (1975), and some rhythmically, as in KECAK; the superimposition of trills, tremolos and harmonics contributes to the more complex texture of his later works.
He has been commissioned from many overseas' music festivals and ensembles such as ULTIMA Contemporary Music Festival Oslo, Octobre en Normandie, Arditti Quartet, Kronos Quartet, ELISION Ensemble, Hannover Society of Contemporary Music and so on.
He at present a Professor at the Tokyo College of Music and the Musical Director of the Izumi Sinfonietta Osaka.