Complex sentence: From 1912 he was again Kapellmeister in Hamburg, but resigned in 1914 and went to Darmstadt as general music director while also often conducting in the U.S. for the Boston Opera Company between 1912-1914.
Split into simpler sentences: From 1912 he was again Kapellmeister in Hamburg, but resigned in 1914 and went to Darmstadt as general music director. He also frequently conducted for the Boston Opera Company between 1912-1914.