Typically the top (the instrument’s soundboard) is made of quarter-sawn spruce, bookmatched at a strongly glued joint down the center, with two sound-holes (or “f-holes”, from their resemblance to a stylized letter “f”) precisely placed between the C-bouts and lower corners. The sound-holes affect the flex patterns of the top, or table, and allow the box to breathe as it vibrates. A decorative inlaid set of three narrow wooden strips, usually a light-colored strip surrounded by two dark strips, called purfling, runs around the edge of the top, and is said to give some resistance to cracks originating at the edge. It is also claimed to allow the top to flex more independently of the rib structure. Some instruments have two lines of purfling, or have knot-work type ornaments inlaid in the back. Painted-on faux purfling on the top is usually a sign of an inferior instrument. A slab-sawn bass bar fitted inside the top, running lengthwise under the bass foot of the bridge, gives added mass and rigidity to the top plate. Some cheaper mass-produced instruments have an integral bass bar, carved from the same piece as the top. Ideally the top is glued to the ribs and linings with slightly diluted hide glue, to allow future removal with minimal damage.
Back and ribs
The back and ribs are typically made of maple, most often with a matching striped figure, called “flame.” Backs may be one-piece slab-cut or quarter-sawn, or bookmatched two-piece quarter-sawn. Backs are also purfled, but in their case the purfling is less structurally important than for the top. Some fine old instruments have scribed or painted rather than inlaid purfling on the back. The small semicircular extension of the back known as the “button” provides extra gluing surface for the crucial neck joint, and is neglected when measuring the length of the back. Occasionally a half-circle of ebony surrounds the button, either to restore material lost in resetting the neck of an old instrument, or to imitate that effect.
The ribs, having been bent to shape by heat, have their curved shape somewhat reinforced by lining strips of other wood at the top and bottom edges. The linings also provide additional gluing surface for the seams between the plates (top and bottom) and the rib edges.
The neck is usually maple with a flamed figure compatible with that of the ribs and back. It carries the fingerboard, typically made of ebony, but often some other wood stained or painted black. Ebony is considered the preferred material because of its hardness, beauty, and superior resistance to wear. Some very old instruments were made with maple fingerboards, carrying a veneer of ebony. At the peg end of the fingerboard sits a small ebony or ivory nut, infrequently called the upper saddle, with grooves to position the strings as they lead into the pegbox. The scroll at the end of the pegbox provides essential mass to tune the fundamental body resonance of the instrument. Some “scrolls” are carved representations of animal or human heads, instead of the classical spiral volute most normally seen.
The maple neck alone is not strong enough to support the tension of the strings without distorting, relying for that strength on its lamination with the fingerboard. For this reason, if a fingerboard comes loose (it happens) it is vital to slacken the strings immediately. The shape of the neck and fingerboard affect how easily the instrument may be played. Fingerboards are dressed to a particular transverse curve, and have a small lengthwise “scoop”, or concavity, slightly more pronounced on the lower strings, especially when meant for gut or synthetic strings. The neck itself is not varnished, but is polished and perhaps lightly sealed, to allow ease and rapidity of shifting between positions.
Some old instruments (and some made to appear old) have a grafted scroll, or a seam between the pegbox and neck itself. Many authentic old instruments have had their necks reset to a slightly increased angle, and lengthened by about a centimeter. The neck graft allows the original scroll to be kept with a Baroque instrument when bringing its neck to conformance with modern standard.
The bridge is a precisely cut piece of maple, preferably with prominent medullary rays, showing a flecked figure. The bridge forms the lower anchor point of the vibrating length of the strings, and transmits the vibration of the strings to the body of the instrument. Its top curve holds the strings at the proper height from the fingerboard, permitting each to be played separately by the bow. The mass distribution and flex of the bridge, acting as a mechanical acoustic filter, have a prominent effect on the sound.
Tuning the instrument can cause the bridge to lean, usually toward the fingerboard as the tightening of the strings pulls it. If left that way, it may warp. Experienced instrumentalists know how to straighten and center a bridge.
The tailpiece may be wood, metal, or plastic, and anchors the strings to the lower bout of the instrument by means of the tailgut, nowadays most often a loop of stout nylon monofilament which rides over the lower saddle, a block of ebony set into the edge of the top, and goes around the endpin. The endpin fits into a tapered hole in the bottom block. Most often the material of the endpin is chosen to match the other fittings, for example, ebony, rosewood or boxwood.
Very often the A string will have a fine tuning lever worked by a small screw turned by the fingers. Fine tuners may also be applied to the other strings, and are sometimes built in to the tailpiece. Fine tuners are usually used with solid metal or composite strings that may be difficult to tune with pegs alone; they are not used with gut strings, which have greater flexibility and don’t respond adequately to the very small changes in tension of fine tuners. Some instrumentalists, particularly beginners or those who favor metal strings, use fine tuners on all four strings. Using a single fine tuner on the A string, or using built-in-tuners, limits the extent to which the tuners’ added mass affects the sound of the instrument.
At the scroll end, the strings ride over the nut into the pegbox, where they wind around the tuning pegs. Strings usually have a colored “silk” wrapping at both ends, for identification and to provide friction against the pegs. The peg shafts are shaved to a standard taper, their pegbox holes being reamed to the same taper, allowing the friction to be increased or decreased by the player applying appropriate pressure along the axis of the peg while turning it. Various brands of peg compound or peg dope help keep the pegs from sticking or slipping. Peg drops are marketed for slipping pegs. Pegs may be made of ebony, rosewood, boxwood, or other woods, either for reasons of economy or to minimize wear on the peg holes by using a softer wood for the pegs. Attempts have been made to market instruments with machine tuners but they have not been generally adopted.