Hard Rock, exploding onto the scene in the late 1960s and early 1970s, evolved from the amplified sounds of blues rock and psychedelic rock, establishing a heavier, more aggressive musical foundation. It's defined by its powerful, often distorted electric guitar riffs, which are central to both melody and rhythm, coupled with driving, thunderous drums and prominent bass lines. Vocals in hard rock often range from gritty, blues-infused shouts to soaring, anthemic deliveries, emphasizing raw energy and passionate expression. This genre masterfully balances catchy, accessible hooks with an undeniable sonic power, forging an essential link between classic rock and the emergence of heavy metal, with legendary acts like Led Zeppelin, Deep Purple, AC/DC, and Van Halen epitomizing its enduring appeal.