Body size, shape and style has changed over time. 19th century guitars, now known as salon guitars, were smaller than modern instruments. Differing patterns of internal bracing have been used over time by luthiers. Torres, Hauser, Ramirez, Fleta, and C. F. Martin were among the most influential designers of their time. Bracing not only strengthens the top against potential collapse due to the stress exerted by the tensioned strings, but also affects the resonance characteristics of the top. The back and sides are made out of a variety of timbers such as mahogany, Indian rosewood and highly regarded Brazilian rosewood (Dalbergia nigra). Each one is primarily chosen for their aesthetic effect and can be decorated with inlays and purfling.
Once you know the basic chords, it might be easier to think of them the way the function inside a key. For example, when in the key of E, the E (I) is called the Tonic. It's what all the other chords want to get to—which is what helps give western music its sense of motion. The A (IV) in the key of E functions as the Subdominant—it's sort of a passive in-between, just as happy to continue forward, as to relax back to the Tonic. The Dominant is just what it sounds like: it leads you where it wants to go. In the key of E, that role is filled by the B (V), and will definitely make your brain want to get back to the Tonic! When you get more familiar with the chords, and want to sketch out a tune, try writing it as I-IV-V (or variations of that) instead of E-A-B. It will make it much easier to transpose when you find out your singer cannot sing in the original key!
Further simplifications occur for the regular tunings that are repetitive, that is, which repeat their strings. For example, the E-G♯-c-e-g♯-c' M3 tuning repeats its octave after every two strings. Such repetition further simplifies the learning of chords and improvisation;[71] This repetition results in two copies of the three open-strings' notes, each in a different octave. Similarly, the B-F-B-F-B-F augmented-fourths tuning repeats itself after one string.[73]
As with most chords in this list, a clear G major chord depends on curling your first finger so the open fourth string rings clearly. Strum all six strings. Sometimes, it makes sense to play a G major chord using your third finger on the sixth string, your second finger on the fifth string, and your fourth (pinky) finger on the first string. This fingering makes the move to a C major chord much easier.
You can tell whether or not strings are of a thin or thick gauge based on the numbers on the package. The smallest number, which is the gauge of thinnest string, will usually be .9 or lower on thin gauge strings. On thick gauge strings this number will be .12 or higher. Strings that are .10 or .11 are generally considered to be “mediums”, and produce a tone and feel which is the middle ground between these two extremes.
The three notes of a major triad have been introduced as an ordered triplet, namely (root, third, fifth), where the major third is four semitones above the root and where the perfect fifth is seven semitones above the root. This type of triad is in closed position. Triads are quite commonly played in open position: For example, the C-major triad is often played with the third (E) and fifth (G) an octave higher, respectively sixteen and nineteen semitones above the root. Another variation of the major triad changes the order of the notes: For example, the C-major triad is often played as (C,G,E), where (C,G) is a perfect fifth and E is raised an octave above the perfect third (C,E). Alternative orderings of the notes in a triad are discussed below (in the discussions of chord inversions and drop-2 chords).

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