Depending upon one’s musical taste the term guitar can evoke any one of four distinct types: classic, flamenco, plectrum or electric. These in turn can be divided into two distinct classes: the nylon string class (classic and flamenco) and the steel string class (plectrum and electric). Those of the first, almost identical in outline, have a couple of basic differences. For example, assuming that both instruments are standard models, the classic is the larger (though not by much) and heavier of the two. The classic’s heavier weight (rosewood back and sides, spruce top) tends to make its tone deeper than the flamenco guitar’s (sycamore back and sides, cedar top).Another difference, and the most physically discernable, lies in the head. The head of the classic guitar houses metal tuning mechanisms, keys and rollers; the flamenco head contains simple tuning pegs made of wood, similar for example to those on a lute but facing downward. There is also at least one other differentiation—pickguards. Unlike the flamenco the classic does not have or need a pick guard, or tapping plate. This is because the percussive effects (rapping) so frequently employed on the flamenco are only rarely used on the classic, and even then are not so harshly executed.
The two types of guitar in the second class are much more varied and dissimilar to each other than those in the first. The electric alone comes in two different forms: the solid body electric, most popular among rock musicians, and the acoustic body electric, favored by jazz players, each of which, especially the former, comes in a host of different styles and colors. The basic stylistic options, however, are limited to two types of design—single or double cutaway of the upper bout. Of course the solid body electric can be cut in almost any design imaginable. It does not really even need a partially guitaristic body since, unlike with the plectrum and to some extent the acoustic body electric, it does not (at least in practical terms) produce any of its sound from the relationship of strings to wood. Its strings are brought to life only by electrical means. And for this reason perhaps, along with some of its more arcane switches and gadgets, the solid body electric would more accurately be described as a music synthesizer with frets rather than a guitar. Here the plectrum guitar, in so far as its shape is concerned—figure eight body, centered sound hole, head—and the fact that it is non-amplified (though of course it can be easily modified with a pick up) has more in common with the classic guitar than with the electric. The plectrum guitar is either flat- or arch-topped. In the first one the strings are fastened to and end on the bridge; in the second the strings go over the bridge nut and are secured to a metal brace (like that on a violin).
Compared to the nylon string guitars plectrums produce a much fiercer resonation and hence are much louder and more “twangy.” The plectrum guitar was at one time mostly used as an accompanying instrument in folk tunes and as a rhythm instrument in big bands. As a band instrument it gradually fell into decline with the advent of the electrified form, which made it not only more practical for background but for the first time allowed the guitar to be a lead instrument on a par with the trumpet and piano.