Complex sentence: Rubbra's musical output included eleven symphonies, four string quartets, three concertosorchestrated as well as orchestrating Brahms' well-known Variations and Fugue on a Theme by Handel in 1938.
Split into simpler sentences: Rubbra's musical output included eleven symphonies, four string quartets, and three concertos. He is well-known for having orchestrated Brahms' Variations and Fugue on a Theme by Handel in 1938.