Kalevi Aho String Quartets 1-3 Stenhammar Quartet BIS   Kalevi Aho (1949-) is a prominent Finnish composer whose oeuvre includes a number of orchestral and chamber works and a smaller body of vocal music. His string quartets are from relatively early in his career, the first from quite early, written when he was only eighteen. All three are included on a BIS recording made by the Stenhammar Quartet, a group from Sweden.    The pieces are presented out of order, beginning with the second quartet, which was written in 1970, during his studies with Einojuhani Rautavaara at the Sibelius Academy