My materials are chosen for beauty, structural integrity and tonal character. Mostly this is reflected in my choice of tonewoods, but it is also reflected in my choice of tuners, nuts and saddles, etc. While the choice of tonewoods affects the sound, the design and sensibilities of the builder have a much greater impact. With that said, it is important to select high quality wood that will allow the guitar to last for generations.
The soundboard in particular needs to be extremely well quartered to resist the tension of the strings over time. While you may be familiar with the terms: AAA, AAAA, Master Grade, etc., these terms are defined by individual suppliers and do not correspond with any universal standard. That is why I work with a small group of select suppliers with high standards that I can trust.
Woods chosen for the back and sides of the guitar have a subtler effect on sound, therefore aesthetic preferences can play more of a role in their selection. As with the soundboard, the most important attributes affecting tone are density, stiffness, and resonance. Resonant woods such as the rosewoods and mahoganies will have a clearer, more ringing tone, while less resonant woods such as walnut and to some extent Koa will have a nuanced “woodier” tone. Denser woods such as ebonies and rosewoods will reinforce the low end, while less dense woods such as mahogany will enhance the midrange and high end. Of course, different woods have a mix of these attributes and variations within some species of woods can be considerable.