A luthier is a craftsperson who builds or repairs string instruments, such as violins or guitars, and is not directly related to watchmaking or horology.
In watchmaking, the term 'luthier' occasionally refers to craftspeople who work on the acoustic components of striking complications—particularly the gongs and resonating structures of minute repeaters, sonneries, and carillons. The parallel to musical instrument making (a luthier traditionally makes stringed instruments) is apt: these specialists tune the gongs and adjust case resonance to achieve harmonious, musical tones rather than harsh strikes.
Gongs in repeater watches are tuned by carefully filing or grinding their length and cross-section to adjust their fundamental frequency. Longer gongs produce lower pitches, shorter ones higher. The gong attachment point to the movement plate also affects tone quality—case material (gold, platinum, steel) changes acoustic properties significantly. Master repeater specialists spend years developing the skill to achieve the clear, harmonious, bell-like tones that distinguish the finest repeater watches from mediocre ones.
Patek Philippe employs dedicated acoustic specialists for their minute repeater and sonnerie watches. Breguet, Jaeger-LeCoultre, and A. Lange & Söhne maintain similar expertise in their ateliers. Independent masters including Philippe Dufour (whose Simplicité sonnerie is legendary), F.P. Journe, and Akrivia's Rexhep Rexhepi have produced acclaimed striking watches. The knowledge is rare—only a handful of people worldwide can tune and assemble world-class repeater mechanisms.