One of the nice things about Steve Reich's music until now has been that it didn't really bother a person. It sort of hung there between the speakers like wallpaper. If you wanted to, you could examine it closely; if not, it supplied a not-unpleasant background to whatever you were doing. It was a static sort of music: tight little patterns (again like wallpaper), repeating (like wallpaper) endlessly (like wallpaper), with a wallpaper-like limitation on the variety of its colors at any given point.

There was progress, of course. If you soaked up about two minutes at the beginning of a Reich piece, then picked up your stylus and moved it about 10 minutes farther in, you would hear the same music significantly developed -- richer and more expansive, as a rule -- through microscopic changes introduced over a long period. It had a kind of hypnotic power if you focused in closely and joyfully absorbed each change (perhaps the addition of another drum, the further enrichment of a chord, the expansion of a phrase) as it came along.

"Tehillim," which will have its Washington premiere this weekend, marks a significant change in the composer's style. In contrast to "Four Organs" or "Music for 18 Musicians," its motifs are loose and expansive -- full-fledged melodies with a rather Middle Eastern flavor. It introduces contrasts of tempo and dynamics more striking than any of his previous works, particularly in the third movement, which is the first really slow one he has composed since his student days. Above all, it has a text: four passages in Hebrew from the Book of Psalms ("Tehillim"), joined by the work's four movements to form a rather elaborate doxology. Sample passages: "The heavens declare the glory of God; Turn from evil and do good, seek peace and pursue it; Praise him with drum and dance, praise him with strings and winds . . . Hallelujah!"

The use of a text (also for the first time since student days) is Reich's explanation for the change of style. "The basic reason for avoiding repetition in 'Tehillim' was the need to set the text in accordance with its rhythm and meaning," he says in his liner notes. The further question of why he chose a text that imposed these requirements is not discussed, but it fits in neatly with the current trend (observable everywhere but particularly in the arts) of returning to the past, trying to re-establish contact with roots and looking for new forms (usually variations on old forms) that communicate easily. Those who are involved in such a quest may find a special interest in Reich's approach to it. ON RECORD, ON STAGE THE ALBUM STEVE REICH Tehillim (ECM-1-1215). THE CONCERT TEHILLIM Washington premiere, conducted by George Manahan, Saturday at 8 at the Pension Building, 440 G Street NW. 783-0690.