In 1969, Curulewski joined the Chicago-based band TW4, featuring college friends
Dennis DeYoung,
Chuck Panozzo, and
John Panozzo. The group evolved into
Styx by 1972. Curulewski was described by tour manager Jim Vose as "the rebel of the group". Just after the recording of the album
Equinox in 1975, Curulewski left Styx to spend more time with his family, and was replaced by
Tommy Shaw. One big factor in Curulewski's departure was an argument between John and DeYoung after a concert. Curulewski had
laryngitis, and tried to cancel the show despite having around 10,000–12,000 people in attendance. After the concert finished and the band went backstage, DeYoung told Curulewski "I never want to go onstage with you again", to which he replied, "Okay, then I quit." == Personal life and death ==