A subculture of rock music that incorporates features such as diverse timbres, unusual time signatures, classical and jazz influences, and lenthy, multi-part songs. Progressive rock arose in the late 1960s as art-school-trained musicians sought to expand the rock genre and break away from the usual conventions.
Although progressive rock is not an electronic music genre per se, its drive to expand rock's instrumental pallett led to the introduction and widespread use of electronic instruments and recording techniques in rock. Starting with the Hammond organ and combo organs in the 1960s, some of the progressive musicians (generally the ones more inclined towards what was called "art rock") gradually introduced the Mellotron circa 1970 and then synthesizers in the early '70s. Progressive keyboard players such as Keith Emerson, Tony Banks, and Rick Wakeman brought in performance synths (and in Emerson's case, a modular synth and popularized the "keyboard stack", often consisting of a piano or Hammond organ with several synths on top, or the now-familiar A-frame stand with synths at several levels, somewhat like a pipe organ console. (In fact, it was the progressive players who led to the phrase "play keyboard"; prior to that time, keyboard players in popular music usually played piano or organ, seldom both, much less additional keyboards.) Most of these players had keyboard chops and combined fast solo runs with complex harmonies and unusual effects, although they were not always the most inventive at patching (Emerson being a noted exception). Some performers relied on patch programming specialists such as Sound Arts' Dan Wyman to handle the electronics and timbre-building end of the job.
Progressive rock had its heydey in the 1970s. It was rejected by the punkers at the end of the decade, although some of its values wound up coming full circle with the New Wave bands who started with punk and then brought the synths back in. The genre has continued and actually enjoyed something of a revival beginning in the mid-1990s, and synths continue to be a major part of it. Dream Theater's Jordan Rudess is a well-known contemporary player in the genre.