Mendelssohn: Complete String Quartets Cedille Records 90000 082 (3 CDs) May 2006 By Richard Wigmore After long being relegated to the second division, Mendelssohn's six mature string quartets are finally getting their due as the greatest quartet cycle between Beethoven and Bartok. The early A minor Op 13 of 1827 is an astonishing, impassioned response to the challenge of Beethoven's late quartets, then usually regarded as beyond the pale. The more classically conceived Op 44 quartets are dazzlingly inventive, while the late F minor Op 80, composed in the wake of his sister's death, has a violence and anguish that may shock those who still view Mendelssohn as a genteel lightweight.   Until recently, the benchmark recording was the Melos Quartet on DG (415 883-2, 3 CDs): vigorous performances that make up in ardour what they lack in tonal finesse. Over the past three or four years, though, the bar has been raised by several younger groups. At super-budget price you would not go wrong with the robust Henschel Quartet (Arte Nova 82876 64009-2, 3 CDs), though in their determination to avoid sentimentality they can push ahead too resolutely in the slow movements.   For performances with an ideal Mendelssohnian blend of fire and grace, my vote would go to the Chicago-based Pacifica Quartet. The delicacy and finesse of their playing - say, in the scurrying night-ride of a scherzo in Op 44 No 3 - are breathtaking.   In fast movements, the Pacifica are always acutely responsive to Mendelssohn's distinctive brand of restlessness; and where the composer demands four virtuosos, as in the outer movements of the E minor Op 44 No 2, they yield to no one in brilliance. But their playing is equally memorable for its tenderness and colouristic subtlety, not least in the poignancy of the F minor's adagio, Mendelssohn's requiem for his beloved sister.