Windham Hill Records, the fast-rising folk-jazz label from San Francisco, showcased three of its more popular artists at the Wax Museum Wednesday night. Pianist George Winston, guitarist Alex De Grassi and pianist Liz Story illustrated the label's chief virtues: a pristine sound, strong melodic figures, intricate variations and solid technical playing. They also betrayed the label's chief liability: a tendency toward simplistic romanticism that can lapse into vague mood music.

Actually, the most disappointing set came from Winston, the label's best-selling artist. His solo piano pieces did feature striking melodic themes and thick, atmospheric harmonies. Winston's improvisations, however, usually settled for the easiest choices and gradually frittered away the listener's interest with repeating phrases. His self-indulgences were highlighted by a pointlessly long version of "Autumn" and two mediocre harmonica solos. Winston's gift for melody and transitions worked best when combined with humor, as on the Fats Waller-influenced "Cat and Mouse."

By contrast, Story kept her pieces under much firmer control structurally and technically. She kept her endlessly varied right-hand melodic figures symmetrically balanced against her rolling left-hand chord progressions. Though this balance seemed a bit static on her lesser compositions, it developed a dramatic tension on her best pieces such as "Solid Colors" and "Bradley's Dream."

The evening's best set was the middle one by De Grassi, who played one-man guitar duets. With his left hand dancing back and forth across the frets, he was able to keep two distinct voices going on the guitar at all times. The lower voice was not just a simple bass line, but was a full chordal foundation for the agile melody variations in the high voice. On "Slow Circle," the two voices seemed to chase each other; in "Inverness," a third voice--a high harmony--appeared at times. Story joined De Grassi's two guitar voices for his "Trio Waltz." As in both their sets, there was little improvisation--just an impeccably handled intricate arrangement of a catchy melody.