become rare collector's items. Six Degrees of Inner Turbulence (2001–2002) Putting the whole ordeal behind them, Dream Theater once again entered BearTracks Studios to record their sixth studio album. Four years after they first petitioned East West to allow them to release a double album, they finally got their chance with Six Degrees of Inner Turbulence. The first disc consisted of five tracks of 7–13 minutes in length, and the second disc was devoted entirely to the 42-minute title track, which remains to date the longest song Dream Theater has written. Many of the song's melodies and musical themes originated in an instrumental piece, written by Rudess, which would eventually become the song's "Overture". Those themes were then expanded by the rest of the band to form individual chapters in a complete story. Six Degrees of Inner Turbulence was very well received by critics and the press. It was the most publicized of Dream Theater's albums since Awake, debuting on the Billboard charts at No. 46 and the Billboard Internet charts at No. 1. The subsequent world tour included a select few special "album cover" gigs (see Cover songs section, below), in which they played Metallica's Master of Puppets and Iron Maiden's The Number of the Beast in their entirety. Train of Thought (2003–2004) In 2003, Dream Theater entered the studio to write and record another album. Unlike Scenes from a Memory, which had been written and recorded simultaneously in the studio, the band took a different approach by setting aside three weeks for writing prior to recording. In the middle of the recording sessions for the album, a special tour with two other progressive metal bands, Queensrÿche and Fates Warning, was undertaken in North America. Referred to in the band's promotional material as the "Escape from the Studio American tour", the tour featured Queensrÿche and Dream Theater as co-headlining acts with Fates Warning performing supporting act duties. As a finale for each concert there was an extended encore in which both Dream Theater and Queensrÿche performed together on stage simultaneously, often playing cover songs. At the completion of the tour, Dream Theater returned to the studio to finish the recording of their seventh album, Train of Thought. In contrast to the extended songs of their previous album, the band aimed to write a more song-oriented album, inspired in part by covering the Master of Puppets and Number of the