Adjusting the truss rod affects the intonation of a guitar as well as the height of the strings from the fingerboard, called the action. Some truss rod systems, called double action truss systems, tighten both ways, pushing the neck both forward and backward (standard truss rods can only release to a point beyond which the neck is no longer compressed and pulled backward). The artist and luthier Irving Sloane pointed out, in his book Steel-String Guitar Construction, that truss rods are intended primarily to remedy concave bowing of the neck, but cannot correct a neck with "back bow" or one that has become twisted.[page needed] Classical guitars do not require truss rods, as their nylon strings exert a lower tensile force with lesser potential to cause structural problems. However, their necks are often reinforced with a strip of harder wood, such as an ebony strip that runs down the back of a cedar neck. There is no tension adjustment on this form of reinforcement.
The fingerboard, also called the fretboard, is a piece of wood embedded with metal frets that comprises the top of the neck. It is flat on classical guitars and slightly curved crosswise on acoustic and electric guitars. The curvature of the fretboard is measured by the fretboard radius, which is the radius of a hypothetical circle of which the fretboard's surface constitutes a segment. The smaller the fretboard radius, the more noticeably curved the fretboard is. Most modern guitars feature a 12" neck radius, while older guitars from the 1960s and 1970s usually feature a 6-8" neck radius. Pinching a string against a fret on fretboard effectively shortens the vibrating length of the string, producing a higher pitch.
Another class of alternative tunings are called drop tunings, because the tuning drops down the lowest string. Dropping down the lowest string a whole tone results in the "drop-D" (or "dropped D") tuning. Its open-string notes DADGBE (from low to high) allow for a deep bass D note, which can be used in keys such as D major, d minor and G major. It simplifies the playing of simple fifths (powerchords). Many contemporary rock bands re-tune all strings down, making, for example, Drop-C or Drop-B tunings.
Left-handed players sometimes choose an opposite-handed (mirror) instrument, although some play in a standard-handed manner, others play a standard-handed guitar reversed, and still others (for example Jimi Hendrix) played a standard-handed guitar strung in reverse. This last configuration differs from a true opposite handed guitar in that the saddle is normally angled in such a way that the bass strings are slightly longer than the treble strings to improve intonation. Reversing the strings, therefore, reverses the relative orientation of the saddle, adversely affecting intonation, although in Hendrix's case, this is believed to have been an important element in his unique sound.
The musical theory of chords is reviewed, to provide terminology for a discussion of guitar chords. Three kinds of chords, which are emphasized in introductions to guitar-playing, are discussed. These basic chords arise in chord-triples that are conventional in Western music, triples that are called three-chord progressions. After each type of chord is introduced, its role in three-chord progressions is noted.
For the standard tuning, there is exactly one interval of a major third between the second and third strings, and all the other intervals are fourths. The irregularity has a price - chords cannot be shifted around the fretboard in the standard tuning E-A-D-G-B-E, which requires four chord-shapes for the major chords. There are separate chord-forms for chords having their root note on the third, fourth, fifth, and sixth strings.
SFCM produces some of the most successful and influential classical guitarists in the world. Spearheaded by renowned faculty and complemented by visiting artists such as Marcin Dylla, the department honors the tradition of the classical guitar while cultivating innovation. The Harris Guitar Collection, housed at SFCM, gives students a chance to see—and play—some of the most extraordinary guitars of the last two centuries.