Chords are notes played together to add colour, depth, and complexity to music. A chord can consist of two notes or many notes; played simultaneously, or in succession to each other. When a chord is played the notes that form it are usually resonant and pleasing to the ear but, there are chords in which the combination of notes create tension, anticipation, or some other subjective emotional response in the listener.
There are dozens of chords for each key signature. For example, there is an "A Major" and an "A Minor" chord, but there are many more chords related to the key of "A". These additional chords are signified by letters, numbers, and abbreviations, which are used in various combinations to signify other chords related to a particular key (like "A"). The table in Figure 3-1 shows just a few of the chords for the key of A.
One of the first things most people learn when they begin playing guitar is "Standard Chords". Standard chords are those chords played within the first three or four frets and they usually involve four or more strings. Most standard chords consist of a different finger formation or configuration, with each of your fingers on a different string. Figure 3-2 shows the standard major, minor and seventh chords for E, F, G, A, B, C, and D (The "natural" music keys).
Major chords are constructed by using the 1st (root), 3rd, and 5th note in a scale. If a chord consists of those three elements alone it is called a triad. Due to the fact that it is possible to play more than 3 notes simultaneously - guitar chords (like piano chords) often include doubles of some notes. Often the octave of the 1st (or root) note is added and sometimes the octave of the 5th note of the root's scale is added to give the chord more strength and depth. You can learn more about "octaves" and "scales" in the lesson: Scales
There are many other standard chords including 9ths, 11ths, 13ths, and more, for each major and minor key. Not to mention the sharps and flats of each "natural" key. You can play many songs using only the standard chords, but using only these few chords does limit the depth and power of your music. Some genres of music, like pop, rock, and heavy metal - and some songs in particular - require a more robust and consistent sound to give them the energy and amplitude that define them. That is where barre chords come in handy. You will learn about "BARRE CHORDS" in the next lesson.