Peter Green

Rock is a broad family of popular music centered on amplified instruments, a strong backbeat, and song forms that foreground riffs, choruses, and anthemic hooks. Emerging from mid‑20th‑century American styles like rhythm & blues, country, and gospel-inflected rock and roll, rock quickly expanded in scope—absorbing folk, blues, and psychedelic ideas—while shaping global youth culture. Core sonic markers include electric guitar (often overdriven), electric bass, drum kit emphasizing beats 2 and 4, and emotive lead vocals. Rock songs commonly use verse–chorus structures, blues-derived harmony, and memorable melodic motifs, ranging from intimate ballads to high‑energy, stadium‑sized performances.

Electric blues is a postwar evolution of the blues that centers on amplified instruments and a compact, urban band sound. It emerged when rural blues musicians brought their music to industrial cities and adopted electric guitar, amplified harmonica, bass, drums, and piano to cut through noisy clubs. Musically, electric blues relies on 12‑bar and 8‑bar forms, dominant‑7th harmony, and a swung shuffle or boogie groove. Guitarists use string bends, wide vibrato, double‑stops, turnarounds, and call‑and‑response with vocals and harmonica. Amplified harmonica (often through a bullet mic and small tube amp) acts like a lead horn, trading riffs with the guitar. The sound is thick, gritty, and vocal, with tube‑amp breakup, subtle reverb, and sometimes tremolo. Lyrically, themes cover migration, love and betrayal, work and hardship, and the pulse of city life. Regionally, Chicago became the emblem of the style, but strong variants also blossomed in Memphis, Detroit, and Texas.

Blues is an African American musical tradition defined by expressive "blue notes," call-and-response phrasing, and a characteristic use of dominant-seventh harmony in cyclical song forms (most famously the 12‑bar blues). It is as much a feeling as a form, conveying sorrow, resilience, humor, and hard-won joy. Musically, blues commonly employs the I–IV–V progression, swung or shuffled rhythms, and the AAB lyric stanza. Melodies lean on the minor/major third ambiguity and the flattened fifth and seventh degrees. Core instruments include voice, guitar (acoustic or electric), harmonica, piano, bass, and drums, with slide guitar, bends, and vocal melismas as signature techniques. Over time the blues has diversified into regional and stylistic currents—Delta and Piedmont country blues, urban Chicago and Texas blues, West Coast jump and boogie-woogie—while profoundly shaping jazz, rhythm & blues, rock and roll, soul, funk, and much of modern popular music.