A beginner's guide to progressive rock in five essential albums

A beginner's guide to progressive rock in five essential albums

As the drug-fuelled experimentation of psychedelia waned after the Summer of Love, bands either went heavy, like Led Zeppelin, Deep Purple or Black Sabbath, or retained a spirit of musical adventure, marrying seemingly ill-matched sounds originally heard on Sgt. Pepper, Pet Sounds and Frank Zappa's Freak Out! and adding some symphonic or classical flourishes. Add a tidy amount of musical prodigiousness, and progressive rock was born. Of course i…