Burton C. Bell (Fear Factory vocalist) and Dave Mustaine (Megadeth vocalist/guitarist), who joined the band on stage to perform parts of the song. Dream Theater later departed from Gigantour 2005 a few dates before it ended and continued on with their own series of concerts, several of which were recorded and released for the band's fanclubs. The 20th anniversary tour concluded with a show at Radio City Music Hall in New York City on April 1, 2006. Though the show had minimal promotion, it was sold out days after tickets were made available. This show, which was recorded for a CD/DVD called Score released on August 29, 2006, through Rhino Records, featured songs from the band's entire history, as well a second half accompanied by a full symphony orchestra (the "Octavarium Orchestra"). This release was the band's third Live DVD release to be certified Platinum in the US on October 11, 2006. Systematic Chaos and Greatest Hit (...And 21 Other Pretty Cool Songs) (2006–2008) For the first time in their career, the band decided to take the summer off after their show at Radio City Music Hall. In September 2006, Dream Theater entered Avatar Studios to record their follow-up to Octavarium with legendary studio engineer Paul Northfield. Dream Theater's ninth studio album, Systematic Chaos, was released on June 5, 2007. The record marked their first with new label Roadrunner Records, which in 2010 would become a wholly owned subsidiary of the band's previous label Atlantic Records. Roadrunner implemented increased promotion for the album and Systematic Chaos duly reached number 19 on the Billboard 200. It also oversaw the release of a video for "Constant Motion" on July 14, the band's first music video since Hollow Years in 1997. The album was bookended by the two parts of "In the Presence of Enemies", written and conceived as a single piece but split into two halves for the purposes of the album. The other six tracks included the most recent part of Portnoy's continuing AA Saga with the song "Repentance". In the same year, the first version of Rich Wilson's Lifting Shadows, an authorized history of the band's first twenty years, was released. The 2007–08 Chaos in Motion Tour started off in Italy. Dream Theater played in the Gods of Metal concert on June 3, 2007, as well as various other European festivals including the Netherlands' Fields of Rock Festival, UK's Download