Bluegrass

Bluegrass is an all-acoustic descendant of old-time and country, typically played by a five-piece string band: mandolin, five-string banjo (Scruggs-style three-finger roll), fiddle, flat-top guitar and upright bass, often with a resophonic Dobro. Tempos commonly sit between 120 and 180 BPM. Songs cycle through arranged choruses and instrumental 'breaks' where each player takes a 16-bar solo in turn, jazz-style. Vocals stack a lead with a high tenor harmony above and sometimes a baritone below, producing the piercing 'high lonesome sound' associated with the genre.

The style is named for Kentucky mandolin player Bill Monroe's Blue Grass Boys, who formalized the sound between 1939 and 1945. The classic lineup crystallized when banjoist Earl Scruggs joined in late 1945, bringing the three-finger picking pattern that still defines the instrument. After Flatt and Scruggs split off in 1948 the music spread through radio barn dances and festival circuits across the Southeast. The 1960s urban folk revival, the soundtrack to the 2000 film 'O Brother, Where Art Thou?' and the rise of Alison Krauss & Union Station in the 1990s each triggered a new wave of listeners. Progressive players such as Béla Fleck and Chris Thile (Punch Brothers, Nickel Creek) have since extended the vocabulary into jazz and chamber composition.

Track the rotation of instrumental breaks — each soloist gets exactly the same number of bars and the rest of the band has to drop to a polite background. The banjo's rolling triplets, the mandolin's tremolo on sustained notes, and the fiddle's slurred double-stops all sit on top of an upright bass that walks 1-5-1-5 like a metronome. In a tight band the vocal harmonies lock so closely they sound like a single voice with overtones.

Start with Bill Monroe & His Blue Grass Boys' 'Blue Moon of Kentucky' (1947). For an instrumental showcase, Flatt & Scruggs' 'Foggy Mountain Breakdown' (1949) demonstrates the banjo style that defined the genre. For a modern entry point, Alison Krauss & Union Station's 'New Favorite' (2001) won three Grammys.

Bluegrass is the only major American genre named after a band: 'Blue Grass Boys' was Bill Monroe's tip of the hat to Kentucky, the Bluegrass State. Earl Scruggs developed his three-finger roll independently in his teens; once captured on record it became impossible to play professional banjo any other way.