Rock ‘n’ roll functions on many different layers. From its earliest days, when country and R&B converged into a wilder hybrid, to its evolution over the decades, including punk, metal, and roots, rock ‘n’ roll has never had a single shade.

But it’s all part of the natural progression. The blues-based rockers of the ’60s gradually gave way to heavier music mid-decade; bands such as Yardbirds, Cream, and the Jimi Hendrix Experience laid the foundations for a new sound that would dominate much of the ’70s: hard rock.

As you will see in the list below of the Top 35 Hard Rock Albums of the ’70s, even this singular subgenre has offshoots and is not easily defined. (Our criteria? We know it when we hear it.) From leftover pieces of the previous decade to the birth of heavy metal, hard rock music has always had more textures than it lets on. A line between Who’s stately rock operas and AC/DC’s bad-boy boogie isn’t always obvious, but dig deep enough, and a pattern will begin to reveal itself.

READ MORE: Top 100 Rock Songs of All Time

Familiar names appear frequently, more than once or twice, in UCR staff’s selection of the Top 35 Hard Rock Albums of the ’70s. Led Zeppelin, Aerosmith, and Black Sabbath place several records in the upper half; there are even some surprises among the candidates.

Yet they share rock ‘n’ roll’s basic structure, amplified by the force of their music, especially through the guitars at the center. For better or worse, hard rock became something else in the decades that followed. But in its ’70s glory, music was rarely as exciting or as significant to the genre’s development.