In 1965, invited by fellow German-born bass player Nick St. Nicholas (born Klaus Kassbaum), Kay joined a blues rock and folk music group known as The Sparrows, which had moderate success in Canada before moving to California, augmenting its line-up, and changing its name to Steppenwolf in 1967. With music that pioneered hard rock and heavy metal, Kay's Steppenwolf had international success with songs such as "Born to Be Wild", "Magic Carpet Ride", "Monster", "The Pusher", and "Rock Me".[citation needed]
Kay recorded both as a solo artist and with Steppenwolf during the late 1970s, and wrapped up Steppenwolf's 40th year of touring with what was to be a final gig in October 2018. Kay and Steppenwolf appeared on 24 July 2010 at the three-day HullabaLOU music festival in Louisville, Kentucky.[7]
In 2004, although he never became a Canadian citizen,[1] Kay was inducted into Canada's Walk of Fame in recognition of the beginning of his musical career in Toronto. Kay was present at the induction ceremony in Toronto and reiterated his strong affection for Canada.[8] He was also nominated as part of Steppenwolf for induction into the Rock and Roll Hall of Fame in 2016 for the induction year 2017.[9] In 2018, Steppenwolf's "Born to Be Wild" was one of the first five record singles to be inducted into The Rock n Roll Hall of Fame.[10]