Complex sentence: John Henry Hammond (December 15,1910--July 10,1987) was a talent scout, record producer, musician and music critic from the 1930s to the early 1980s, and one of the most influential figures in 20th Century popular music.
Split into simpler sentences: John Henry Hammond (December 15,1910--July 10,1987) was a record producer, musician and music critic from the 1930s to the early 1980s. In his service as a talent scout, Hammond became one of the most influential figures in 20th Century popular music.