from guide: Guitar Wood Types and Tones (Body, Body top, Neck, Fretboard)

Chapter 2.Guitar Body Top Woods

Tops seem to create a situation where the attack of the notes will be more like the top wood, while the resonance and decay more like the bottom wood. The thickness and carve of a top dictates the degree of its effect on the sound. The glued unit will be more rigid than a single piece, so generally sustain increases.

Maple top:

Maple top on Basswood:

The clean attack and even highs of Maple will make up for Basswood's inherent reduction of those frequencies. The lows will still taper off, but the overall result is more frequencies covered than with either piece alone. Dynamics aren't reduced, except for in the upper register, where they were less present in Basswood alone. So the improvement in high response is a little more compressed, and not as crisp and responsive in the attack as Swamp Ash for example.

Maple top on Mahogany:

The most popular couple nowadays. The staple of vintage construction, the Maple adds crispness to the mahogany, but the lows and low mids of mahogany are still as apparent. The Maple combs out some of the upper mids, not because Maple lacks in these areas, but because it is vastly different from mahogany in its handling of the upper midrange. There is fighting going on in that range between the two pieces that results in a canceling out of some of those upper midrange frequencies. That's part of the "smoothness" associated with the Les Paul & PRS types. Although figured maple is more visual estetique, some guitarists like Mark Knopfler guess regular maple sounds smoothly.

Maple top on Alder:

Takes Alder to a tone closer to solid Swamp Ash, but without the dynamics. The open resonance of the Alder comes through with the sharper attack and brightness of the Maple on the top end. The effect on the Alder is similar to the effect on Basswood. The upper mids of Maple come through, as Alder does not suppress upper mids.

Maple top on Swamp Ash:

A good addition to Swamp Ash but reduces the open, airy dynamics of solid Ash. It mutes the expanded midrange, but doesn't really comb out any sections. They work well together. It adds a little more rock and country compressed "scream" to the sound at the expense of Ash's complex lows and low mids.

Rosewood tops:

Rosewood tops will add some sustain, by virtue of the density, but also the lamination itself. Its oiliness will dampen the attack and the higher treble frequencies. So Rosewood over Mahogany will really be smooth, while Rosewood over Ash will retain some open midrange resonance. Rosewood over Alder or Basswood will be a sustain boost with little affect on the tone besides the high mid combing from the lamination, since the high dampening from Rosewood is redundant.

Koa tops:

Figured or plain Koa tops will sound similar to Maple tops with the exception being that it wouldn't fight Mahogany backs so much in the upper midrange. Although Maple resonates more upper mids, a Koa top on Mahogany would have less combing and compressing of those frequencies.

Walnut tops:

Like Koa, the tops would have just a little less high frequency than Maple, but have less compression and combing with Mahogany backs.

Lacewood tops:

Lacewood has a hard "swiss cheese" type skeleton, with soft bits inside the "holes." Because of its combination of soft and hard sections, it's more likely to take on the tone of the back wood. Only when thicker will it start to apply its own tonal signature to the body. It's like drilling ?" holes in Koa and filling them with Alder plugs. It has good top end and sustain from the harder skeleton, and a heavily combed midrange and low end from the smaller, softer sections throughout.

Learn more about Body, Body Tops, Necks and Fretboards at guide: Guitar Wood Types and Tones