A word about tone woods. I can't speak to how the new materials work, but among standard woods, there is a large difference, no matter the shape or size of the guitar.

Mahogany (Martin's "18" designation -- spruce top, solid mahogany sides and back). Dry, punchy tone, with a chime on top. The best of them is a great instrument for "cutting through" a group of instruments. Typically, the least expensive solid wood.

Rosewood (Martin's "28" -- spruce top, rosewood sides and two-piece back) gives a deeper, rounder, but sometimes mushier sound. The bluegrass player's favorite rhythm instrument is the D-28, and it does a fine job of filling out the sound. Among folksingers, Tom Paxton's early recordings shows how the rosewood sound provides a bakdrop for vocals.

Maple (Not a a "traditional" Martin material) gives you the sharpest, zingiest, sometimes too-bright sound. I've heard some maple guitars that nearly make the ears bleed with their sharp, treble-enhanced sound. That said, my regular playing guitar (a Running Dog Jumbo from Rick Davis -- recommended!) is spruce on sycamore, and that wood is a maple of sorts, but the sound is much fuller and complex than maple, with the dryness of mahogany and the 'bloom' of rosewood. I love it.

Other woods and configurations of woods are used (the Martin '35' has a three-piece back of rosewood, and is enough different from the two-piece back of a 28, even if no other changes are made.

Rick Davis, among other makers, uses cherry, walnut, and (my favorite, as I said above) sycamore.

Each wood has its own sound, and, coupled with body size and shape, neck material, and bracing patterns, provides just about any sound you want to hear.

And no one has even mentioned the Ovation!

Bob