for their psychedelic and space rock music, and later, as they evolved, for their progressive rock music. Pink Floyd are known for philosophical lyrics, sonic experimentation, innovative album cover art, and elaborate live shows. One of rock music's most successful acts, the group have sold over 210 million albums worldwide including 74.5 million albums in the United States alone. Pink Floyd influenced progressive rock artists of the 1970s such as Genesis and Yes, as well as contemporary artists such as Nine Inch Nails and Dream Theater.