The 12-tone system does afford a certain melodic brilliance, while sacrificing harmoniousness in the major and minor thirds and sixths. This creates the restlessness mentioned previously, and it does not permit much subtlety. All the tempered scales will have their own biases, moods, and personalities, so that the composer's tastes and the intended moods of the music will influence the choice of scale. The just scale, with its major thirds that sound more harmonious than those found in the equal temperament system, theoretically includes more possibilities for harmonic variety when extended over a large enough range, but then we must deal with the physical limitations of the guitar, such as its slightly less than four-octave range. There is obviously a limit to the number of frets that can be placed on a fingerboard, since they will eventually grow together into a solid sheet of metal, making the instrument fretless again.
Some scales lack what is described in classical terminology as consonant, or agreeable, chords.
And while they may have melodic value, the harmony-oriented guitarist will probably pass them over. A guitar with a movable bridge faciIitates experimentation with one of these systems. This will give an approximation of the 13-tone equal temperament. Though all the intervals are strange and wacky, the melodic possibilities may intrigue you. By experiments such as these, it is possible to narrow down the number of systems to be considered for fretted instruments to a reasonable figure.