Now back to examining wood as it's used in guitar construction.
To the untrained eye of a non player the neck of a guitar appears to be one long piece of wood but of course it is not. Except for a very few electric guitars like the Fender Stratocasters with maple necks, guitar necks consist of two or more pieces. There are a few reasons for this. All modern guitars have some sort of metal or graphite brace between the main part of the neck (the mahogany I talked about last time) and the much thinner, flat portion with the frets, which we know as the fingerboard. It is much easier for the guitar maker to bevel out the mahogany, place the brace in, then glue a fingerboard in place than to try to drill a long hole in a single piece of wood and then push in the brace.
The two woods used almost always for fingerboards are rosewood and the more expensive ebony. Some guitar makers including Martin have begun using man-made materials for fingerboards on their less expensive instruments. You have to look very, very closely to determine a Martin has a "micarta" fingerboard (although you can always check the list of materials used via their web site). The non wood fingerboards I've played all look and feel just fine - very hard and dense material is used - but some purists object to something other than wood being used. I guess part of me agrees but if it means companies can keep some of their guitars at a more reasonable cost by doing so, more power to them.
Rosewood works well for fingerboards. It is hard wood but is easier to work with than ebony and is less prone to cracking over the long run. Some guitarists prefer the slightly softer feel of rosewood to ebony too. It looks quite beautiful and ages well.
Ebony is the premier wood for fingerboards but it is more expensive than ever, as fine hardwoods become harder to find. There have been a few unfortunate attempts to use different varieties of ebony including something called "striped ebony" which in some cases bled into the tops of guitars. This didn't happen on all the guitars made with the stuff (primarily in the 1990s) but it happened often enough for makers to give up on it.
You will also see some fingerboards that are "bound" with white plastic (in the old days it was ivory). It makes a very nice look but if you're considering a guitar with a bound neck, know that a re-fret job will cost you twice as much as with a guitar with an unbound neck. This is because the luthier must carefully shape the ends of the frets to fit over the binding.
Speaking of such things, you will certainly see some amazing inlay jobs on fingerboards. Most "regular" inlay consists of small round or diamond shaped pieces of mother of pearl (or plastic on cheaper guitars) but inlay is often where a custom guitar maker can really express his creative energy. My feeling is that it can go way overboard at times however. As much as I love Martins, the top of the line 45-series instruments have just too much bling for me, but of course there is no accounting for taste and many guitarists absolutely love guitars with tons of inlay. It has no effect on sound or play-ability though, assuming a good, careful job was done.
Bridges are very similar to fingerboards in materials with rosewood and ebony being most common. You will see some more exotic woods used for bridges occasionally, stuff like African Blackwood. Bridges must be made of hard, dense material to transmit the vibration of the string to the top of the guitar. The micarta stuff is used for bridges too by Martin, and many, many of the inexpensive guitars coming out of Korea, China and other parts of the Far East use plastic, which is often colored with "grain" like lines to imitate wood. I do think that wood bridges are superior to plastic ones in terms of sound.
Tops of acoustic guitars are a very complicated subject and the area where most of the luthiers' skills come into play. Usually made of spruce of some sort (Sitka, Adirondack, German, Italian) tops of guitars must be sawn, glued, braced and finished with the utmost care. This is where the tension of the strings becomes a source of wonderful resonance or destructive power. Spruce is a relatively soft wood, which is why it is used: those vibrations are transmitted through it very well and the top must vibrate to produce the sounds we love. Straight grain must be used to evenly transmit vibration although some guitarists love the look of "bear claw" in their guitar tops - wavy, almost 3-D variations in certain places on the top, as if a bear sharpened his claws on the tree from which the wood was cut! Whether it has any effect on the sound is open to debate but a top with a lot of "bear claw" is highly desirable on an expensive guitar.
The wood of the top should be "bookmatched" - this means two pieces that were cut in sequence, then glued together down the center so the grain variations are identical on either side of the top.
On inexpensive guitars it was once common to use laminated wood for tops and although much easier to work with and less expensive than solid wood, most players agree that guitars with laminated tops don't sound anywhere near as good as ones that are solid. That being said, there is a small but vocal group who are obsessed with early/mid 1970s Yamahas, which had laminated tops and these folks claim they sound every bit as good as guitars with solid tops. I can tell you that back then I had access to new Yamahas for my students and I sold well over 100 of them. Maybe, maybe one in twenty sounded ..... pretty OK. Not great, but pretty OK. But hey, what do I know? Today, "red label" Yammies from that era are bringing 4 - 6 times what they sold for when new! No accounting for taste, as I said earlier!
Some guitars are made with cedar tops. This is an interesting wood to use because it is somewhat softer than spruce and vibrates more, which is why it is often used on very high-end classical guitars. With steel strings, which exert much more pressure than nylon strings, extra care must be taken by the guitar maker to brace cedar tops in such a way that they can resonate well but do not crack or warp. The Taylor company has some beautiful guitars that fit this description.
So that's it as far as wood goes. I'm sure if you asked around or did some research you would find opinions that vary from the ones I've expressed in my last three entries. But just like the wood itself, there is a lot of variety in how players feel about the stuff that makes our guitars such magical things!
Peace & good music,