Led Zeppelin were never a group of settlers. Their previous album, IV virtually defined the hard rock genre with its era-defining guitar riffs and bombastic destiny. It remains among rock’s essential albums. The follow-up never tries to emulate that achievement. Instead, Houses of the Holy approaches things from a diverse, genre-busting side. “The Song Remains the Same” opens things at their leisure, opting for a dense guitar-heavy maelstrom that soon gives way to the meditative seven-and-a-half minutes of “The Rain Song.” Guitarist Jimmy Page and bassist-keyboardist John Paul Jones work in lockstep, weaving mystical passages (the shivering mellotron-heavy “No Quarter”), dynamic acoustic/electric rock (“Over the Hills and Far Away”), reggae (“D’Yer Maker”) and both pseudo-funk (the James Brown homage “The Crunge”) and their own legitimate brand of groove rock (“The Ocean,” “Dancing Days”) always with a sense of musical space that allowed each instrument to shine individually and work within the context of the group. Led Zeppelin mastered each genre they attempted. They never shied from a new idea. And they often succeeded brilliantly with each risk.