The band played a brand of progressive rock with pop music leanings, as opposed to the hard rock approach of The Flower Kings or the metal feel of Dream Theater. In 2002, the band released a rock opera entitled Snow, whose story and themes bear a strong resemblance to that of The Who's Tommy. Many listeners and critics have noted the parallels between the storyline of Snow and Neal Morse's own highly-publicized conversion to Christianity.
Following the release of Snow, Neal Morse left the band to concentrate on spiritual matters. Drummer Nick D'Virgilio took over the lead singing and songwriting role, in a move reminiscent of Genesis drummer Phil Collins taking over from Peter Gabriel. Their first album, Feel Euphoria, has a harder rocking and more experimental sound than the Neal Morse-led band, relying on Alan Morse's guitar to a greater extent.
The band was named for the Star Trek episode "Mirror, Mirror", where the crew enters a parallel universe in which the parallel Mr. Spock is differentiated by his beard.
Neal Morse also participated in the prog supergroup TransAtlantic.