CROSSINGS -HQ-With the frenzied knocking of what sounds like a clock shop gone berserk, Crossings takes the Herbie Hancock Sextet even further into the electric avant garde, creating its own idiom. Now, however, the sextet has become a septet with the addition of Dr. Patrick Gleeson on Moog synthesizer, whose electronic decorations, pitchless and not, give the band an even spacier edge. Again, there are only three tracks the centerpiece being Hancock's multi