Complex sentence: He felt that music was the least developed of all the arts in Iceland he co-founded the Reykjavik Music Society which, under his helm for over half a century, brought many of the world's greatest names in classical music into Iceland.
Split into simpler sentences: He felt that music was the least developed of all the arts in Iceland. He co-founded the Reykjavik Music Society which, under his helm for over half a century, brought many of the world's greatest names in classical music into Iceland.