Complex sentence: In the mid- 1940s, Luboff moved to New York City to expand his musical horizons but it would be in Hollywood where he would achieve national fame, doing the choral and vocal arrangements for a number of motion pictures.
Split into simpler sentences: In the mid- 1940s, Luboff moved to New York City to expand his musical horizons but it would be in Hollywood where he would achieve national fame. Luboff did the choral and vocal arrangements for a number of motion pictures.