Dream Theater，堪称是90年代以来最重要也最具代表性与影响力的前卫金属乐团，其92年所发表的专辑《Images and Words》，为当时的金属乐开创出新的表现形式，专辑中高层次的技术展现，使得团员纷纷成为各方注目的焦点，也使得这张专辑顺理成章地成为前卫金属史上的经典代表作，也是所有前卫金属乐迷奉为「圣经」的必备专辑。
Dream Theater成立於80年代中期，最初的团名为Majesty，由三位出自美国波士顿著名的Berklee音乐学院的吉他手John Petrucci、鼓手Mike Portnoy、bass手John Myung，再加上keyboard手Kevin Moore所组成。1986年3月，主唱Chris Collins加入DT，并录制了一张demo。然而由於Chris的嗓音无法胜任DT的要求，不久离开了DT。87年新任主唱Charlie Dominici加入，团名也正式更换为Dream Theater，同年11月发行了具有历史意义的第一张专辑《When Dream And Day Unite》。专辑具有极佳的音乐性和技巧性，并已展露出DT特有的编曲特色，然而这张专辑却是叫好不叫座，惨淡的销售成绩使乐团面临多方面的问题。由於主唱的音色和演唱实力仍然无法与DT的音乐相契合，於是被要求离去。
91年新任主唱James Labrie加入乐团，其出色的音色和厚实的嗓音与DT成为完美的搭配，至此DT可算是有了最完整的阵容。果然，在92年的专辑《Images and Words》推出后获到相当大的回响，不仅将乐团的声望带上高峰，也正式宣告前卫金属时代的来临！
在这张专辑中，所确立的复杂编曲样式、吉他键盘对弹，以及丰富多变的节奏，无一不成为日后大多数新生代乐团所仿效的对象。Petrucci快速流畅的吉他技巧令人赞叹，keyboard手Kevin Moore深厚的弹奏实力，在专辑中如《Take the time》、《Under a glass moon》等歌曲里，都展示了与吉他对拍竞飙的绝佳风范，而在《Another day》、《Surrounded》曲中却也有著极其柔美而令人动容的抒情手腕。鼓手Mike Portnoy灵活且复杂多变的鼓点，总是带给听者无比的惊奇感(光看他的鼓具就觉得很不可思议)。而bass手John Myung则同样身手不凡，除了与鼓紧密搭配，也能和吉他键盘做对弹。当然主唱James Labrie的演唱功力与乐团的搭配也只能用「完美」来形容了！
94年第三张专辑《Awake》的推出，可说更确立了Dream Theater在前卫金属乐界王者的地位。此张专辑延续前一张《Images and Words》的技术导向，并更上一层楼。不仅编曲极为复杂，在篇幅上亦增长不少，其中还包含了近三十分钟的三乐章式串连组曲，堪称是一部绝作！一般第一次接触到这张专辑的人，或许会觉得乐曲过分冗长且艰深难懂，然而对於所有前卫金属的乐迷来说，这张专辑无疑是一部极品中的极品，值得细细去品味。在我听了这么多的前卫金属专辑后，回过头来再听这张专辑时，依然还是再次地被感动。在我心目中，大概很难再找到一张作品能超越《Awake》的技术表现及其成就了！
不过，令人遗憾的是，在94年8月，keyboard手Kevin Moore由于音乐方向上的分歧而离开DT(后来跑去Fate Warning，并参与专辑《A Pleasant Shade Of Gray》，目前已自组乐团Chroma Key)，此一空缺在几经波折后，确定由新任的keyboard手Derek Sherinian入替，让人不禁为DT未来的发展感到忧心。
95年所发表的EP《A Change of Seasons》，除了第一首《A Change Of Seasons》为创作曲外，其他四首则是收录自一次在英国伦敦Ronnie Scott's Jazz Club的现场演出。其中有三曲分别为翻唱自Elton John、Deep Purple及Led Zeppelin的作品，而第五首《The Big Medley#10:34》更是取自Pink Floyd、Kansas、Queen、Journey、Dixie Dregs、Genesis六首歌所混合而成的组曲，藉由这几首翻唱的曲子，算是表达了DT对这些陪伴他们成长的老前辈们的敬意。 长达23分钟的同名曲《A Change of Seasons》，是由七个段落所组成的叙述长篇曲，戏剧性的编曲、丰富的情感，加上畅快的旋律实在令人荡气回肠！这种深沉的感觉似乎是在DT过去的作品中所不曾听到的，这也预示着DT的成熟期的即将来临！
沈寂了两年的Dream Theater，在全球前卫乐迷的引颈盼望下，终於在97年10月推出了第五张的正式专辑《Falling Into Infinity》。然而这张专辑的推出却得到了极端两极化的评价。相较於之前的作品，此张专辑的风格改变相当地大，不再完全只侧重於乐器编曲与技巧的高复杂度，反而更加重了整体气氛的营造与旋律的优美感，同时音色上则变得较为沉重。在keyboard方面，新任的Derek Sherinian表现十分称职，不同於以往keyboard与吉他并重的突出表现，在此张专辑中不强调keyboard的solo，而是在音色的润饰与气氛的营造上下了相当多的功夫。不过，DT过去的一些表现手法和精神依旧是继续存在的，如专辑中的《Just Let Me Breathe》，正是延续过去专辑的复杂特色，快速流畅的吉他弹奏，厚重的bass与大量变拍的鼓点，keyboard亦展现了与吉他对飙的能力，整体的表现仍维持在《Awake》时期的水准。而《Hell's Kitchen》与《Lines In The Sand》两首共16分钟的乐曲及末尾13分钟的《Trial Of Tears》则再次展现DT在长篇幅编曲上的功力。演奏曲《Hell's Kitchen》不但相当优美且气势磅礴，《Lines In The Sand》兼具了重量感与优美旋律，而《Trial Of Tears》全曲由三个段落所组成，并一气呵成，这首乐曲指明了Dream Theater试图前行的新方向。
然而，并不是所有的乐迷都能接受DT这样的改变，有人认为这张专辑已经变了味道，不再是过去所熟悉的Dream Theater了。特别是keyboard手Derek Sherinian个人对於键盘音色的偏好，也使DT的新作显得十分沈重；另一方面，有人则乐于看见DT有这样的改变。因为一个乐团不能永远一陈不变，否则终会陷入窠臼。而对我来说，虽然我也喜欢这张专辑，不过我还是很怀念过去的DT。听惯了《Images and Words》的人可能得花点时间才能适应这张专辑了！(或许无法适应？)
在FII专辑发行后，吉他手John Petrucci和鼓手Mike Portnoy乘著空档的时间，邀来了King Crimson的bass手Tony Levin，与Dixie Dregs的keyboard手Jordan Rudess合组了一个project乐团Liquid Tension Experiment，并在98年发表了同名的演奏专辑。这张专辑的推出立刻受到了极广大的好评！专辑中展现了在DT过去的作品中所鲜少听到的活泼作风与丰沛情感，四位音乐大师尽性地挥洒与相互激荡，没有太多刻意的雕琢，一切都是那样地自然而令人动容！
另一方面，Bass手John Myung与keyboard手Derek Sherinian也没有闲著，亦组了project乐团Platypus，并出版了专辑《When Pus Comes To Shove》。
在LTE这张专辑成功的合作经验后，DT的成员也深刻认识到到Jordan Rudess的作曲编曲能力对他们的影响；另一方面，在DT的成员之中，显然keyboard手Derek的作风与DT的风格不太符合，实力也是最弱的一环，於是Jordan Rudess也正式取代Derek Sherinian成为新任的keyboard手，DT也希望Jordan Rudess的加入能让他们走向新的里程！
99年，DT的团员可说动作频频，project乐团Liquid Tension Experiment继续推出了第二张的专辑，此外，主唱James LaBrie也以project乐团的形式发表了个人专辑《Mullmuzzler/Keep It To Yourself》，这两张专辑都属必备级！
不过，真正的高潮好戏在99年末才上演！Dream Theater的第6张录音室作品《Metropolis Part 2: Scenes From A Memory》在10月底正式推出，这张专辑的发表再次引起前卫金属界的极大震撼！原本认为《Awake》这张作品已是最高境界的极致之作，想不到新生的DT再次超越了自我！在历经了LTE两张专辑的洗礼后，Dream Theater以这张长达70多分钟的长篇概念式专辑做为世纪末迎接千禧的最佳献礼，果然不愧为前卫金属之王！再次由衷地赞叹！伟哉！梦剧院！
The technically proficient guitar playing of John Petrucci elevated Dream Theater to the upper echelons of contemporary heavy metal. While its lineup has continuously evolved, the Long Island-based quintet has consistently delivered sharp-edged music. Dream Theater is known for its high-energy concert performances. While they've released several live albums -- Live at the Marquee, recorded at the London club; Live in Japan, recorded during the Music in Progress tour in 1993; and a triple CD and DVD, Live Scenes from New York -- they remain one of heavy metal's most bootlegged bands.
Originally named Majesty by Berklee College of Music students Petrucci, bassist John Myung, and drummer Mike Portnoy, the band soon expanded with the addition of keyboard player Kevin Moore and vocalist Chris Collins. Releasing an eight-tune demo, Majesty Demo, as Majesty, the group sold 1,000 copies within six months. The departure of Collins in late 1986 left Majesty without a vocalist, and after a long period of auditioning possible replacements, the group settled on Charlie Dominici in November 1987. Changing its name, the group agreed on "Dream Theater," inspired by a now-demolished California movie theater. Signing with Mechanic Records, the group began working on its first full-length album. Delays caused by label mismanagement limited the group to performing at small clubs and bars. Frustrated by its experiences with the label, Dream Theater finally severed its ties with Mechanic.
This was only one drastic change in the band's course of action. Firing Dominici, the group spent the next couple years searching for a vocalist. The search ended in late 1991 when a demo tape from Canadian vocalist James LaBrie, formerly of Winter Rose, arrived. After flying to New York to audition, LaBrie was invited to join the band. Signing with Atco Atlantic (which came to be known as East West), Dream Theater released its second album, Images & Words, in 1992. One of three videos based on songs from the album, "Pull Me Under," became an MTV hit. Although Theater showed considerable growth with their third studio album, Awake, recorded between May and July 1994, the group continued to be hampered by personnel changes. Before the album was mixed, keyboardist Moore left the group to focus on his solo career. Hired as a temporary replacement for the band's Waking Up the World tour, Derek Sherinian later became a permanent member. His first recording with Dream Theater was a 23-minute epic, "A Change of Seasons," written in 1989 and released in September 1995 on the album of the same name.
Following a mini tour, Fix for '96, the members of Dream Theater separated for several months and became involved with a variety of outside projects. Petrucci was the busiest. In addition to joining Portnoy and keyboard player Jordan Rudess in the Liquid Tension Experiment -- a group that included influential bassist/stick player Tony Levin -- Petrucci played guitar with Trent Gardner's Explorers Club and made a guest appearance on Shadow Gallery's Tyranny album. Myung and Sherinian collaborated with King's X vocalist Ty Tabor in the band Platypus. LaBrie worked with Mull Muzzler, a group formed with Matt Guillory and Mike Mangini.
Dream Theater experienced yet another change when Rudess was tapped to replace Sherinian, who had been fired in 1999. The band released the progressive rock-heavy Scenes from a Memory that year, a conceptual piece that followed the story of a 1928 murder of a young woman and how a modern man is haunted by the crime. It was followed by Live Scenes from New York in 2001, which suffered from an unintentional bout with controversy when its original cover featuring the city of New York in flames was pulled due to the events of September 11. The group continued in the progressive metal vein in 2002 with Six Degrees of Inner Turbulence, followed by the leaner Train of Thought in 2003 and Octavarium in 2005. The live album Score: XOX was released in 2006 and featured the band backed by a 29-piece orchestra. It was followed a year later by the new studio album Systematic Chaos.
Sherinian went on to record as a soloist and to play with a prog and jazz fusion band, Planet X. Petrucci released an eponymously titled solo album in 2003, featuring accompaniment by Dave LaRue of the Dixie Dregs and Boston-based drummer Dave DeCenso.