The widespread preference for tropical wood species in guitar neck manufacturing is increasingly challenged by the declining availability of these resources, creating an urgent need for sustainable alternatives. This study compared the deflection stability of 17 wood species used for classical guitar necks under long-term string tension and varying humidity conditions, focusing on the performance of tropical woods and potential European alternatives. The effects of the experimental set-ups (tuning key and weight-loaded device) and wood cross-grain orientations (quarter-sawn and flat-sawn) were also examined. The results indicated that the two tropical wood species, mahogany and cedro, exhibited relatively small and consistent deflection variations, especially under changing humidity. Among the tested European-grown wood species, black walnut and alder showed great potential as materials for guitar necks, with some performance indicators surpassing those of tropical woods, making them viable alternatives. Different experimental setups had no significant impact on deflection measurements, and the tuning key device provided a simpler method for evaluating guitar neck stability. Quarter-sawn neck wood samples demonstrated more stable deflection than flat-sawn wood, though this difference was not significant in the majority of tested wood species. Exploring alternative wood species will expand the material selection of the local musical instrument manufacturing industry and contribute to the sustainable use of local-grown wood resources.