Complex sentence: Alan Rich, music critic of "New York" magazine, having heard a privately issued record of Brown's piano pieces wrote they were just sub-standard re-workings of some of their better-known compositions.
Split into simpler sentences: Alan Rich, music critic of "New York" magazine, took a more skeptical line. Having heard a privately issued record of Brown's piano pieces, Rich concluded that they were just sub-standard re-workings of some of their better-known compositions.