Complex sentence: In 1930 he invented "Gesprochene Musik," the idiom of the "spoken chorus"; his most performed work is the "Geographical Fugue" or "Fuge aus der Geographie", though he regarded it as an unimportant diversion.
Split into simpler sentences: In 1930 he invented "Gesprochene Musik," the idiom of the "spoken chorus". His most performed work is the "Geographical Fugue" or "Fuge aus der Geographie", which he himself regarded as an unimportant diversion.