Schoenberg and Steve Reich notwithstanding, the star of this new-music extravaganza is the Yamaha MIDI grand piano, making its Chicago debut. According to the event's organizer, composer Howard Sandroff, this state-of-the-art instrument, when plugged into a network of microcomputers and digital synthesizers, allows for "the economic use of sound objects and the inventive enhancement of the piano sound." To show off its potential, Sandroff has rearranged a 1984 work of his, now titled Adagio for the Piano, intending "through synthesis and simulation, to create an illusion of static aural objects--variations and the originals--juxtaposed over themselves." In other words, the Yamaha can produce a cubistic effect rarely explored in the piano literature. In charge of the console is pianist Salvatore Spina. Also scheduled for performance are: Schoenberg's trailblazing Pierrot Lunaire (in a new English translation sung by Susan Charles) and that minimalist watershed, Reich's Tehellim (parts one and two), based on the Hebrew psalms of praise. The performers are the New Art Ensemble, an exceptional group affiliated with the Music Center of the North Shore. Tonight, 8 PM, Weinstein Center for the Performing Arts, National College of Education, 2840 Sheridan, Evanston; 446-3822.