YOU CAN HAVE your synthesizers and amplified guitars; the wildest sounds in music right now are being made by a string quartet -- the Kronos Quartet, which will be playing in the Terrace Theater twice this weekend.

The Kronos is a crossover phenomenon, appealing as much to lovers of art rock as to devotees of contemporary classical styles; it chooses material wherever it likes in the whole vast spectrum of music and plays it with gusto, sensitivity and technical precision.

A good example is the latest Kronos album, "White Man Sleeps," on the imaginative, technically excellent Nonesuch label. Even in traditional selections -- Bartok's Third Quartet, an arrangement of "Amazing Grace" by Ben Johnston, and Ives' short, witty "Holding Your Own" -- this high-energy performance should appeal to the listeners who will be attracted first by the material written or arranged for Kronos: two pungent variants of the title number by Kevin Volans, a brilliant arrangement of Ornette Coleman's "Lonely Woman," and a long, elaborate, technically tricky and psychologically evocative piece by Jon Hassell called "Pano da Costa."

One of the best commissioned pieces, "Morango . . . Almost a Tango" by Thomas Oboe Lee (who won the 1983 Kennedy Center/Friedheim Competition), can be heard only on the CD, not the LP or cassette. Throughout, the performances are brilliant and the sound has a larger-than-life presence.

The two Terrace performances will have different programs; Sunday's will feature much of the material from "White Man Sleeps." KRONOS QUARTET --

"White Man Sleeps" (Nonesuch 9 79163). Appearing Saturday and Sunday in the Terrace Theater.