Complex sentence: Apart from a handful of piano preludes and sonatas, Dlugoszewski had written little music prior to 1950, but once in New York, she quickly became a prolific composer of experimental music, including several open-form works.
Split into simpler sentences: Apart from a handful of piano preludes and sonatas, Dlugoszewski had written little music prior to 1950. Once in New York, she quickly became a prolific composer of experimental music, including several open-form works.