At Ravinia this weekend the normally museum-minded CSO will express its belated appreciation of two of the true individualists of this century: Toru Takemitsu and Olivier Messiaen, whose idiosyncratic styles, at first considered exotic or just plain far-out, have recently invigorated the mainstream. Friday’s featured selection, Takemitsu’s concerto Riverrun, epitomizes his preoccupation with nature and water imagery–though he was among the first postwar Japanese artists to embrace cutting-edge Western aesthetics, by the time he’d completed the concerto in 1984, Takemitsu had reclaimed his Japanese roots via John Cage. The ripples, swirls, and cascades in Riverrun flow Zen-like–mysterious, recurrent, at times turbulent, yet ultimately harmonious. The piano soloist will be Peter Serkin, a new-music advocate who has turned this concerto into a crusade for Takemitsu’s place in the pantheon. There are a number of connections between Messiaen and Takemitsu, both stylistic and philosophical, but for you trivia buffs, Messiaen’s Turangalila-symphonie, featured on Sunday’s program, has a special link to Riverrun: it refers to the Arthurian legend of Tristan and Isolde, which James Joyce appropriated in Finnegans Wake, which in turn lends Riverrun its title. Despite the obvious precedent, Messiaen’s monumental ten-movement symphony is only fitfully Wagnerian; the primary source of its inspiration lies East, in Hindu and Balinese music. Its title–a composite of two Sanskrit words that translate as “a hymn to the rhythm of life”–suggests that a variety of rhythmic patterns is in store, and indeed that’s the case; Messiaen relied on a veritable battalion of percussion instruments to approximate a large gamelan. A piano figures prominently, and so does the ondes Martenot, an electronic keyboard instrument from the 20s that’s capable of very low pitches and eerily high-toned glissandi. Here the piano will be handled by Marc-Andre Hamelin, a Canadian specialist in the 20th-century repertoire, and the ondes Martenot by one of its few virtuosos, Jean Laurendeau. The remainder of both programs consists of standard summer fare; Christoph Eschenbach conducts. Friday, 8 PM, and Sunday, 7 PM, pavilion, Ravinia Festival, Green Bay and Lake Cook Rds., Highland Park; 847-266-5100. TED SHEN

Art accompanying story in printed newspaper (not available in this archive): Peter Serkin photo by Regina Tauney; Jean Laurendeau uncredited photo.