Church bells tuning temperament evaluation through spectral acoustic emission matching

• The study investigates tuning temperaments in historical church bells. • Spectral acoustic emission analysis is applied to Salerno Cathedral bells. • Evidence suggests bell tuning followed historical musical temperaments. • Findings redefine the timeline of systematic bell tuning to the 13th century. • Tuning was part of intangible heritage related to bell making. Church bells, as historical artifacts and musical instruments, represent a unique intersection between tangible and intangible elements of cultural heritage. While previous works suggested that systematic bell tuning only emerged in the 18th century, this work hypothesizes and presents experimental evidence indicating otherwise. Focusing on the bells of Salerno Cathedral (Italy), casted between the 13th and 19th centuries, we investigated whether their tuning reference evolved coherently with the historical evolution of Western music theory or followed independent standards. A non-invasive spectral analysis was applied to identify tonal components and compare them with historical musical temperaments. Results show that reference tuning systems were already in use by the 13th century, centuries earlier than previously documented. A consistent evolution in tuning, matching the historical development of temperaments, was also observed. These findings suggest the existence of a non-formalized implicit know-how in bell-making, having important implications for heritage conservation. The proposed approach also provides a preliminary diagnostic tool to support the identification of a church bell features for its functional restoration, supporting the recognition of this know-how as a part of the intangible heritage related to church bells.