Chuck Berry established the electric guitar as the primary instrument of rock & roll. He used this guitar for significant recordings and performances in the late 1950s and early 1960s. In 1957, Gibson introduced Seth Lover's patent-applied-for (PAF) humbucking pickups, which has two coils with currents running in opposite directions, canceling (or bucking) an electrical hum that the earlier single-coil pickups could produce. The humbucker-equipped, semi-hollow-bodied Gibsons Berry favored, combined with high-powered Fender amps, produced his iconic big, bold tone. Berry's expressive guitar solos and signature double-note runs led the way for generations of rock guitarists.