Bluegrass music is a subgenre of country music that developed in the Appalachian region. It was pioneered by Bill Monroe and his band, the Blue Grass Boys (named after his home state of Kentucky). Bluegrass is unique because it is purely acoustic and emphasizes instrumental virtuosity and high-pitched vocal harmonies. The standard ensemble includes the mandolin, five-string banjo, fiddle, acoustic guitar, and upright bass. Unlike traditional folk, Bluegrass features 'breakdowns' where each instrument takes a turn improvising at high speeds. The 'Scruggs style' of banjo playing—using three fingers to pick rapid, rolling notes—is a hallmark of the genre. The music blends Irish and Scottish traditional music with African-American blues and jazz elements. It is often referred to as the 'high lonesome sound' because of the strained, emotional quality of the vocals, which often deal with themes of home, faith, and hardship.