Planet X is an evolution of keyboardist Derek Sherinian's 1999 solo album Planet X. Sherinian has stated in several interviews that his intention when forming Planet X was to create a band that "played their instruments so fiercely, that they would strike fear in the hearts of all musicians". Sherinian has called the band's style "metal fusion".

After recording an eponymous solo album, Derek Sherinian (formerly of the progressive metal band Dream Theater) expanded the album's line-up to full time duty in conjunction with drummer Virgil Donati. To date they have released three studio albums and one live CD. On the recorded albums, the band works with multiple guest guitarists. (Tony MacAlpine is the guitarist on the first three Planet X albums - in 2004 he left to tour with Steve Vai).

Planet X's sound is far removed from standard radio fare - Virgil Donati once remarked, "Our most exotic time signature is four." In any one composition, it is not uncommon to hear dozens of time changes. The compositions are strictly instrumental, except for occasional rare spoken words. Taking a page from jazz, most of the songs are extended solo sections punctuated by breakdowns or choruses. However, sonically they bear almost nothing in common with all but the most avant-garde jazz fusion.

Following Universe, Planet X released Live From Oz recorded during their Australian tour in 2002. A full version of the track "Atlantis : Apocalypse 1470 BC" from the CD and the Planet X Web site can be heard here[1]. The next studio release, Moonbabies, was released later that same year. The record was mixed and co-produced by drummer Simon Phillips who remarked that "Planet X is a band that is playing the almost impossible." Guest bassists featured on the release were Tom Kennedy, Jimmy Johnson and Billy Sheehan.

Planet X has toured worldwide including Japan, Australia, Holland, USA, Canada, Poland, Bulgaria and Romania.

The most recent album Quantum released in 2007 features long-time fusion guitarist Allan Holdsworth, guitarist Brett Garsed, who appeared on Sherinian's 1999 solo album Planet X, and bassists Jimmy Johnson and Rufus Philpot.

Source : http://en.wikipedia.org/wiki/Planet_X_%28band%29