Earlier this month, I was fortunate to spend an afternoon at SDSU for a jazz guitar clinic given by Howard Paul, president and CEO of Benedetto Guitars. Howard gave an excellent presentation on the evolution of jazz guitar building practices, complete with demos of seven Benedetto models.
We first looked at the construction of flat top guitars, durable for treks across the country and steel strings for volume. Because the bridge and tailpiece are placed together on the top of the guitar, right in the middle, an incredible amount of bracing is required. The top of any acoustic guitar needs to be delicate enough to vibrate with the strings and project sound like a speaker cone. The tight steel strings of a flat top would rip that delicate top right off without extra bracing underneath it. Unfortunately, that extra bracing reduces the acoustic qualities of the guitar, so it couldn't be heard well in a jazz band setting.
Developments by Gibson and others in the early 1900s brought more traditional stringed instrument designs to the guitar. Like a violin or cello, the top was carved into an arch with f-holes next to the bridge instead of a single round hole under the strings. The tailpiece was attached to the side of the guitar, called a violin or trapeze tailpiece, to provide a downward force on the bridge. Thus, there was no more danger of ripping off the top, so that extra bracing was no longer necessary, which allowed the top to resonate more freely.
Ideally, no holes were drilled anywhere in the top. The tailpiece was attached to the side. The pickguard was attached to the neck, supported by an additional attachment to the side if necessary. When pickups came to prominence in the 30s, they were attached to the pickguard or neck. The volume knob was accessible on the pickguard, and the output jack on the side. In fact, nothing even touched the top of the guitar except the bridge, which was essential in transferring the strings' vibrations to the top.
Built-in pickups were also developed as an alternative to the floating pickup. This required a change in the bracing, which traditionally runs in a big "X" underneath the top. Cutting a big hole or two in the top for pickups requires parallel bracing, running along the sides of the pickups, parallel to the strings. Installing pickups allows for more tonal flexibility while maintaining most, but not the optimum, acoustic qualities. So, with occasional exceptions, a built-in pickup means parallel bracing, and floating or no pickup means x-bracing.
Of course, with pickups and amplification comes feedback, especially with hollow, highly resonant bodies. This leads us to solid bodies, Telecasters, Les Pauls, Stratocasters, and away from traditional jazz guitar.
The finest woods used in jazz guitars come from Europe, specifically spruce and maple. According to Howard, they generally grow on hillsides in harsh environments, leading to tight, stable growth rings. Spruce happens to be optimal for the resonant top, and maple for the reflecting back and sides.
Tops are traditionally hand-carved from two adjacent pie-slices of European spruce, glued together down the center of the resulting guitar. This takes many man-hours and wastes most of the wood purchased for the process. A more cost-effective means of constructing the top comes from laminated sheets of wood, cut from tree trunks in thin spirals. Different wood types can be laminated together, with perpendicular grain directions for stability, in a variety of thicknesses. They are then machine-pressed into the proper shape for a given guitar top. The laminated method results in less expensive guitars, less feedback, but less acoustic quality. The ultimate in jazz guitar construction remains the hand-carved top.
Howard summarized his presentation with a continuum of jazz guitar designs, ranging from the traditional ideal to the more modern sounds of fusion and pop.
On the traditional end:
- designed for acoustic qualities
- hand-carved top
- all European woods, usually spruce and maple
- floating or no pickup
- floating bridge
- trapeze tailpiece
- no holes besides f-holes in the top, nothing touching except bridge
- 17" wide, measured at the widest point of the lower bout
On the modern end:
- laminated top
- 2 pickups, built-in
- parallel bracing or a center block (semi-hollow)
- sometimes no sound holes
- Tune-o-matic bridge
- stoptail bridge
- smaller body
Of course, jazz guitars can fall anywhere on this spectrum, combining features from both ends. My own Epiphone Sheraton II falls squarely on the cheap side, but I still love the sound I get from it. And I love having money to buy food.
For the ultimate detail in jazz guitar construction, see the definitive book on the subject, written by Robert Benedetto himself, Making an Archtop Guitar.