The quality of musical instruments is appreciated not only by their acoustic performance, but also by the surface smoothness, which can be quantified. This chapter presents a study of the effect of two varnishing types, one solvent based (LS) and one oil-based (LU) and of the number of film layers, 5, 10 and 15, on the surface morphologySurface morphology of resonance spruceRadial cuttingresonance (resonance bar, resonance box, resonance spruce) and sycamore maple (straight and curly grain) of two quality classes, specially selected for the manufacture of musical instruments. The results have shown that the LS varnish has increased an anatomical undulation in both species, especially in spruce, which also enhanced the color differences in earlywood-latewood. The crosscut grain in curly maple absorbed more varnish enhancing the colour contrast. LU varnish covered much better the surface irregularities of both species and categories providing a smoother surface, compared to the LS varnish, by 2–3 times for spruce and 6 times for maple, after 10 layers of varnish film. Both varnish categories significantly decreased theSurface roughness surface roughnessRoughness, Rk, in both species after 5 and 10 layers, but 15 layers did not improve the surface qualitySurface quality any further, on the contrary, made the surface susceptible to dust inclusion and scratches.