Hello Troubadourians! Over the years, I have written about numerous things that have an affect on your tone and I have discussed — sometimes in exceeding detail — the methods and devices you can utilize to control, alter, and ultimately optimize your tone. There is, however, one factor of every instrument that is both the foundation of its inherent tonality and completely unalterable. That factor is scale length. What is scale length? Scale length is the distance from the nut to the bridge on a stringed instrument. This definition — and the rules that follow — is applicable to all stringed instruments, but for the sake of simplicity we’ll use the guitar as an example for this article.
On a guitar, each string is stretched between the nut and the bridge and tuned to a particular pitch. When plucked, strummed, or otherwise set in motion, the string will vibrate at the pitch to which it has been tuned and will also generate overtones — tones not the same as the fundamental pitch — which are usually higher in frequency and complementary. This overtone series is characteristic of the scale length and separate from all other overtone sources, such as the wood or other material that the resonating chamber is made of, EQ, pickups, age of the guitar, type of materials in the bridge saddle and/or nut, type of constriction or configuration, and gauge of the string. All of these factors are highly interactive and can influence the aggregate tonality of the guitar but the fact remains that if a frequency is absent from the original signal; it cannot be amplified or attenuated by any secondary agent. What does that mean? It means that two instruments made from the same materials and of the same age, with the same pickups and run through the same EQ and amplification — but with different scale lengths — will always sound characteristically different.
Time for some comparative background. There are a few scale lengths that have become standard for acoustic and electric guitars. These exist partly from tradition or basic physical convenience and partly from carefully executed industrial design or ease of manufacture. The most popular scale length, in terms of the number of instruments produced, is 25 ½” as found on most Fender models, most Martin models, and most classical guitars. The next most popular scale length is probably 24 ¾”, featured on most Gibson guitar models, both acoustic and electric. With these two scale lengths as examples, we have the basis for a general comparison. Back to the most basic components: two strings of a specific gauge, tuned to the same pitch, and stretched between two points, but of different lengths, will sound different. The perception is that the longer the scale, the more the tonality favors higher overtone frequencies. With electric guitars, we often associate this emphasis on higher overtones with the terms “twang” or “jangle.” Manufacturers often choose materials and components for guitars based on a 25 ½” scale to accentuate this natural phenomenon. Maple necks, ash or maple bodies, and single coil pickups combine with the longer scale to create the generic formula for bright sounding guitars with a lot of clarity between individual notes and sharper attack. Guitars based on the shorter 24 ¾” scale tend to be made from materials that accent the “mellow” tonality that is characteristic of this scale. Mahogany necks and bodies and humbucking pickups yield guitars that we think of as sounding “fat” or “warm” and the perception of longer sustain. If you think of Fender Telecasters and Stratocasters as examples of the former and Gibson Les Pauls as examples of the latter, you’ll understand the basic concept. With acoustic guitars, the differences are often more subtle and are often complicated by the different body sizes that are popularly available. However, what follows is an example of the dominance of the scale length over construction materials. A Martin model D-18 is an obvious choice as D-18s are made with mahogany bodies and necks, which we just learned are supposed to sound “mellow,” but in actuality D-18s are most often thought of as sounding bright and articulate. What gives? Well, the D-18, as well as most other Martin guitars including all dreadnought models, are constructed on a 25 ½” scale. By comparison, a Gibson J-200 is often thought of as sounding mellow despite having a maple neck and body. What accounts for this? The J-200 has a 24 ¾” scale length. So why did Martin and Gibson choose to base their instruments on different scales? The answer is mostly because the guitar companies developed from different histories and from different “Genesis instruments.” Martin guitars are derived from classical guitars that traditionally have the longer 25 ½” scale while Gibsons derived from the viol family of instruments, which led to the selection of a shorter scale when the company started building guitars.
There are other by-products of the difference between scale lengths. Given the same gauge of string, a longer scale will feel stiffer than a shorter scale. I have performed many experiments with altering string gauges on guitars of various scale lengths and through calculation of string gauge and tension. I have found that it is possible to make a short scale guitar feel nearly identical to a long scale guitar by installing heavier gauge strings. Likewise, lighter strings can make a long scale guitar feel more like a short scale guitar. More difficult to experiment with is construction type and materials, especially with acoustic guitars. As I stated earlier, different wood types, pickup types, body sizes, and construction materials have different basic tonal characteristics and can be utilized to emphasize a brighter or mellower tone. You can also use amplifiers and EQ to nudge your tone into favoring the “bright-twang” or “fat-mellow” characteristics. If you like the basic tonality of your guitar and when performing usually choose to make it sound “more like itself,” then you’re probably satisfied with the tonality that is germain to the scale length that your guitar is built on. If, however, you find yourself trying to make your guitar sound like some other brand or model of guitar and are constantly changing pickups, electronics, EQ, and anything else you can grab onto to get more twang, more depth, more mellow, more jangle, or whatever, you may be chasing an unobtainable goal and wasting good money on an unsatisfying tone. Perhaps you should investigate the scale length of your instrument vs. that of the instrument whose tone you covet. You may find that your goal is incompatible with your tools.
Need to know? Just ask… Charlie (ask.charlie@hotmail.com)