Pianist Onishi, 27, is a fleet and fearless improviser, a genuine jazz musician who can rethink a classic like Berlin's ''Blue Skies'' or toss off gorgeous instant melodies. On her second American album, she benefits from the great rhythm section of ex-Wynton Marsalis drummer Herlin Riley and bassist Reginald Veal. Onishi's one flaw: occasional muddy sound. B+

