Cyrus signed a four-album deal with Hollywood Records to distribute her non-"Hannah Montana" soundtrack music. She released the two-disc album ' in June 2007. The first disc was credited as the second soundtrack by "Hannah Montana", while the second disc served as Cyrus's debut studio album. The album became her second to reach the top of the "Billboard" 200, and has sold over threemillion copies since its release. Months after the release of the project, "See You Again" (2007) was released as the lead single from the album. The song was a commercial success, and has sold over twomillion copies in the United States since its release. She then collaborated with her father on the single "Ready, Set, Don't Go" (2007). Cyrus embarked on her highly successful Best of Both Worlds Tour (2007–08) to promote its release. Ticketmaster officials commented that "there [hadn't] been a demand of this level or intensity since The Beatles or Elvis". The tour's success led to the theatrical release of the 3D concert film ' (2008). While initially intended to be a limited release, the film's success led to a longer run.