An eighteenth-century French lyre guitar (a variant of the familiar European guitar) was examined and treated during 1995-96. Visual and technical analysis revealed that extensive adhesive and material failure had occurred over-all, leading to sever deformation of the wooden plates comprising the instrument, and the loss of decorative as well as structural elements. The treatment of the instrument relied on a careful balance of conservation and craft techniques and this paper focuses on details of these techniques. The treatment was informed by the multidisciplinary approach inherent in objects conservation, which is ideally suited to the composite (and functional) nature of musical instruments.