Cowgirls contributed to the sound in various family groups. Patsy Montana opened the door for female artists with her history-making song "I Want To Be a Cowboy's Sweetheart". This would begin a movement toward opportunities for women to have successful solo careers. Bob Wills was another country musician from the Lower Great Plains who had become very popular as the leader of a "hot string band," and who also appeared in Hollywood westerns. His mix of country and jazz, which started out as dance hall music, would become known as western swing. Cliff Bruner, Moon Mullican, Milton Brown and Adolph Hofner were other early western swing pioneers. Spade Cooley and Tex Williams also had very popular bands and appeared in films. At its height, western swing rivaled the popularity of big band swing music.