Bout (Upper and Lower) — Lutherie Encyclopedia

Bout (Upper and Lower)Type: glossaryThe curved upper and lower widths of a guitar body, separated by the waist, defining the instrument's silhouette.## Definition The bouts are the wide, curved portions of a guitar or similar stringed instrument body. The upper bout is the section nearest the neck, and the lower bout is the larger section at the bottom of the body. Together with the waist, the bouts define the classic hourglass silhouette of an acoustic guitar. The dimensions of each bout directly affect the instrument's tonal response, volume, and ergonomic feel. A larger lower bout generally produces more bass response and overall volume because the greater soundboard area can move more air. The upper bout contributes to midrange clarity. The ratio between the two, along with the depth of the waist curve, gives each body style its distinctive character: a dreadnought has relatively wide, shallow bouts, while a classical guitar has a more pronounced waist and rounder bouts. ## In Practice When designing or selecting a body shape, luthiers specify bout widths as key dimensions. For example, a typical dreadnought might have a lower bout of 395mm and an upper bout of 290mm, while an orchestral model might measure 380mm and 270mm respectively. The bout dimensions determine the mold shape, which in turn guides the bending of the sides. Builders must heat-bend the side wood to match the bout curves precisely, paying special attention to the tight radius at the waist. The bout shape also influences bracing layout, since wider bouts need more structural support to resist the torque of string tension transmitted through the brid…