In the life of a jazz ensemble, there are plateaus, there are peaks, and there is sometimes something even beyond those: a point of unusual artistic union, which defies description more fiercely than it resists comprehension. That sounds slightly cosmic? Deal with it. Quest reminds me of John Coltrane's quartet in their ability to find the high plane, to illuminate it for listeners, and then to return there on a regular basis. The heart of their success is the long relationship between soprano saxophonist David Liebman--relentlessly scratching each new surface he uncovers as he digs down to the music's core--and pianist Richie Beirach, who has worked with Liebman on various projects for more than 20 years. For Quest, improvisation can attain semimystical proportions: the telepathy that's evolved over their long association is just the springboard for creative somersaults. This is less a band than a continuing seminar in finely tuned synergy. Tonight, 8 PM, Richard Burton Theatre, Triton College, 2000 Fifth, River Grove; 708-456-8383.