In its purest form, Rock & Roll has three chords, a strong, insistent back beat, and a catchy melody. Early rock & roll drew from a variety of sources, primarily blues, R&B, and country, but also gospel, traditional pop, jazz, and folk. All of these influences combined in a simple, blues-based song structure that was fast, danceable, and catchy.

In its purest form, Rock & Roll has three chords, a strong, insistent back beat, and a catchy melody. Early rock & roll drew from a variety of sources, primarily blues, R&B, and country, but also gospel, traditional pop, jazz, and folk. All of these influences combined in a simple, blues-based song structure that was fast, danceable, and catchy. The first wave of rock & rollers -- Chuck Berry, Elvis Presley, Little Richard, Jerry Lee Lewis, Buddy Holly, Bo Diddley, Bill Haley, Gene Vincent, the Everly Brothers, and Carl Perkins, among many others -- set the template for rock & roll that was followed over the next four decades. During each decade, a number of artists replicated the sound of the first rockers, while some expanded that definition and others completely exploded the constrictions of the genre. From the British Invasion, folk-rock, and psychedelia, and through hard rock, heavy metal, glam rock, and punk, most subgenres of rock & roll initially demonstrated an allegiance to the basic structure of rock & roll. Once these permutations emerged, traditional rock & roll faded away from the pop charts, yet there were always artists that kept the flame alive. Some, like the Rolling Stones and the Faces, adhered to the basic rules of traditional rock & roll but played the music fast and loose. Others, like proto-punk rockers the Velvet Underground, the New York Dolls, and the Stooges, kept the basic song structure, but played it with more menace. Still others, like Dave Edmunds and Graham Parker, became rock & roll traditionalists, writing and recording music that never wavered from the sound of the late '50s and early '60s. Although the term "rock & roll" came to refer to a number of different music styles in the decades following its inception, the essential form of the music never changed.

During the mid-'80s, a generation of bands reacted to the slick, pop-oriented sounds of new wave by reverting back to the traditional rock & roll values of the '50s and '60s. By bringing rock back to its roots -- whether that was rock & roll, blues, or country -- the groups managed to sound like a fresh alternative, which brought them critical praise and heavy airplay from American college radio stations. Most of the leading bands of the era -- such as the Beat Farmers, Del Lords, the Long Ryders, and the Del Fuegos -- filtered many of their traditional values through the music of Creedence Clearwater Revival, but there was an equally large number of groups that simply worked in a "rootsy" fashion, without any direct influence outside of the concept of traditional rock and blues. In the late '80s, Roots Rock ceased to be a hip music in the American underground, but most of the bands continued to record and perform into the '90s. Throughout the '90s, a small number of new roots rockers emerged, although they weren't afforded the same exposure as their predecessors.