These are lean times for the jazz vocal field; all the masters are advanced in age, and every time a young jazz singer attracts attention, he or she quickly crosses over to pop. That's why Cassandra Wilson's Washington debut Saturday night at d.c. space was such a landmark, encouraging event. The young, Mississippi-raised singer not only has a magnificent voice with a deep, warm bottom range, but she also has the improvisational instincts of a seasoned jazz musician; she was the one giving the directions and cues to her three excellent musicians Saturday.

Wilson did a few standards -- transforming " 'Round Midnight" and "Body and Soul" with her liquid, note-slurring variations -- but it was her brand-new material that was most exciting. When Wilson added funk and world beat elements to her music, it didn't make it more accessible or more commercial; those modern elements merely made her rich, challenging music more varied. The harmonic intervals were still unpredictable; the rhythms still shifted from verse to verse; her moody, rounded tone still implied a tangled mixture of affection and regret.

With her tidy dreadlocks, strapless red wraparound, bulging eyes and ready laugh, Wilson proved a most charismatic presence onstage. While most jazz singers scat with percussive consonants that sound like a piano, Wilson favored open, note-bending vowels that sounded more like a woodwind. Kevin Bruce Harris played restlessly moving melody lines on an electric bass; Rod Williams punctuated his angular piano phrases with pauses, and Marc Johnson applied a light touch to his rolling drum figures. Their discipline left a lot of space in the music, and Wilson used that space to slowly, softly slide syllables downward across several notes until she found the right emotional ambivalence for her purposes.