Cathal Joseph Patrick "Carl" Smyth (born 14 January 1959, London, England), also known as Chas Smash, is an English musician, best known as the backing singer, trumpet player and dancer in the ska/pop band Madness. In addition to trumpet, he plays bass guitar (having initially joined Madness as a bassist), acoustic guitar and various percussion instruments. He occasionally performs lead vocals, such as on the songs "Michael Caine", "Wings of a Dove", "One Step Beyond and "Madness (Is All in the Mind)". He was initially an occasional songwriter, becoming a more regular contributor over the course of Madness's career, and was credited as co-writer on the group's major international hit, "Our House".
In 1976, The North London Invaders recruited the 17 year old Smyth to play bass until he was replaced in 1977 by Gavin Rogers. Three years later, he became the last of the seven original Madness members to join the band. Prior to that he was a friend of the band and danced onstage at concerts. After Madness broke up in 1986, he formed a new short-lived band The Madness along with Suggs, Lee Thompson and Chris Foreman.