For a number of years the selection of music for each film program rested entirely in the hands of the conductor or leader of the orchestra，and very often the principal qualification for holding such a position was not skill or taste so much as the ownership of a large personal library of musical pieces.

　　(特殊结构not…SO much as…——与其说…不如说…)

　　【译句】在好些年内，为各部影片选择配乐的权力完全掌握在乐队指挥或队长手中，而通常担任这种职位的资格与其说是技巧或鉴赏品位，不如说是个人拥有音乐作品的丰富收藏。

　　分句1：.For a number of years the selection of music for each film program rested entirely in the hands of the conductor or leader of the orchestra;

　　分句2：and very often the principal qualification far holding such a position was not skill or taste so much as the ownership of a large personal library of musical pieces;

　　分句1 和分句2是两个并列关系的分句，分句2的难点在于not…… so much as的结构。