Complex sentence: Joel Mandelbaum (born in 1932) is an American music composer and teacher, most well known for his use of microtonal tuning (notably the Just intonation tuning and the 19ET and the 31ET).
Split into simpler sentences: Joel Mandelbaum (born in 1932) is an American music composer and teacher. He's most particularly known for his use of microtonal tuning (notably the Just intonation tuning and the 19ET and the 31ET).