Towards Digital Twins for Cultural Heritage Musical Instruments: Geometric Documentation and Materials Analysis

Digital twins are emerging as a promising framework for the documentation, analysis, conservation, and interpretation of cultural heritage musical instruments. Their development depends on the integration of accurate geometric information with detailed knowledge of material composition, structure, and condition. This review examines recent progress in these two complementary domains, with particular focus on geometry capture and materials investigation as the foundations of digital-twin development for heritage instruments. The geometric documentation section discusses the main techniques used for digital acquisition, including photogrammetry, 3D scanning, and computed tomography, highlighting their respective capabilities for recording external morphology, internal structures, and analysis-ready digital models. The materials investigation section reviews studies on metallic, wooden, and surface-finishing materials, emphasizing analytical approaches used to identify composition, manufacturing features, degradation processes, and conservation-relevant properties. The review further discusses current challenges, including the relationship between geometry and acoustic behavior, the difficulty of converting raw scan data into usable CAD representations, the limited investigation of mechanical and acoustic material properties, and the constraints imposed by non-invasive analysis. On this basis, the paper argues that digital twins for cultural heritage instruments should be understood not as static 3D reconstructions but as integrated, evolving, and multidisciplinary models capable of combining geometric, material, environmental, structural, and functional information. Such an approach has strong potential to support conservation, monitoring, simulation, replica production, and broader heritage research.