American singer, guitarist and keyboardist best known as a founding member of the rock band Chicago. He is the songwriter behind many of the group's most popular songs, including "Saturday in the Park" and "Does Anybody Really Know What Time It Is?"
He was born in Brooklyn and moved to Chicago at age 15. He later studied in the music program at Roosevelt University.
He has been married four times since 1971.
He and trumpeter Lee Loughnane are two of the founding members of the globally-successful rock band Chicago.