Have you listened to rock songs that are thirty minutes long with three drummers and you need to listen to it fifty times before you get it? That’s progressive rock!!!
Jokes aside, progressive rock or “prog” rock is basically just a complex form of rock. That’s it! Getting familiar with the ingredients that make rock more complex or “progressive” is the best way to understand the genre. Here are some of the most important ones:
Timbre – The instrumentation goes beyond the basic guitar, bass and drums. You’ll find flutes, violins, saxophone, synthesizers, etc…
Form – The structure is more complex than the simple verse-chorus format. You may find classical forms and extended instrumental passages. Songs can be pretty lengthy.
Rhythm – Time signatures other than common 4/4 and tempo changes.
Melody/Harmony – Unusual scales and chord progressions.
Lyrics – You’ll be hard pressed to find a common topic like love. You’ll find a lot of fantasy, folklore or social themes.
Concept – The music, lyrics and album art are unified by a common theme or story.
Technology – Production of this kind of music is usually pushes recording technology to its limits with synthesizers, computers and other inventive tools.
The more you find these elements in the music, the more progressive it is.
With prog rock is best to classify the material and not the artist. Some bands were only progressive for a while like Rush in the 70’s. And then there were bands that released only one or two progressive rock albums like The Beatles’ Sgt. Peppers (considered the first prog rock album) or The Who’s Tommy and Quadrophenia.
The best examples of classic progressive rock of the 70’s are known as The Big Six: Pink Floyd, Genesis, Yes, Jethro Tull, King Crimson and ELP.
There are also other notable bands that were progressive without the excesses like Kansas, Supertramp, Marillion, Styx and ELO.