## 2 Manufacturing Processes of Musical Instruments Made of Composites and Alternative Materials
### Three-Dimensional Printing in Musical Instrument Manufacturing
Despite the difficulties, research on additively manufactured musical instruments has advanced, with a predominant emphasis on wind instruments and, to a lesser extent, string and percussion instruments. Research predominantly focuses on wind instruments due to the costliness associated with their traditional manufacturing methods. The rationale behind this emphasis lies in the fact that the material of a wind instrument has a comparatively lesser impact on the produced sound when contrasted with strings or percussion instruments, as indicated in former studies [5; 43; 44; 45]. Guitars [5; 47; 48], violins [5; 42; 48], flutes [44; 46; 48], claves [49], drums [5], whistles [5], and mouthpieces for wind instruments [35] have all been successfully 3D-printed, with their sound effectively compared to traditionally crafted counterparts. Research in this field extends beyond classical instruments to encompass traditional and even lost musical instruments, either replicated based on descriptions or existing parts. Notably, traditional instruments like the Hawaiian ukulele [43], Greek anakari [45], Japanese shakuhachi [43], and many others were successfully reproduced through 3D printing, producing sounds remarkably like conventionally constructed counterparts. Additionally, efforts were made to revive lost instruments, such as the cornet [37], and to create entirely new ones, like slide pipes [43] (whistle-like instruments), which were 3D-printed and featured in various concerts. In addition to 3D-printed polymers, the potential application of 3D-printed bio-inspired composites has also attracted interest from scientists. Nacre and chitin, among other materials, stand out as promising candidates for bio-inspired composites due to various noteworthy properties they exhibit. [PERSON] et al. [50] conducted a study on 3D-printed nacre, incorporating hollow platelets to achieve good sound absorption, lightweight properties, and mechanical performance. The composite demonstrates a combination of properties, which resemble cellular materials, and the ability to dissipate energy. By extending their previous work, [PERSON] et al. [51], studied the influence of parameters such as geometry, on the attenuation properties of nacre. The wave attenuation properties were also the topic of the study of [PERSON] et al. [52]. Consequently, nacre can be described as a non-brittle ceramic, due to its high strength and high roughness [53]. This enables the use of nacre 3D-printed bio-composites to the crafting of idiophones or parts of other musical instruments. 3D printing technology has profound impacts on the musical industry. It enables the customization of musical instruments, fostering innovation in design and even giving rise to entirely new instruments. Moreover, the potential for mass production using 3D printing has the capacity to enhance accessibility and affordability of musical instruments. Additionally, this technology is instrumental in rapid prototyping and the faithful replication of vintage or rare instruments, contributing to the preservation of musical heritage [5; 43; 45; 54].