Conventionally, guitarists double notes in a chord to increase its volume, an important technique for players without amplification; doubling notes and changing the order of notes also changes the timbre of chords. It can make a possible a "chord" which is composed of the all same note on different strings. Many chords can be played with the same notes in more than one place on the fretboard.
Another factor to consider are the alloys used to make the string. Acoustic strings may be phosphor bronze or an 80/20 bronze/zinc alloy, electric strings may be pure steel or a steel/nickel alloy, and the outer winding on the thicker strings may be either round wound or flat wound, which is typically used by jazz guitarists for smooth fingering with less fretting noise. Acoustic and electric strings are both now available with special super-thin coatings to protect them from sweat and corrosion. Coated strings cost more, but generally last much longer. Find out what type of string your favorite player uses, try guitars with different types of strings at your local guitar store, then try a few different sets on your guitar to see what feels and sounds best for your playing style. Major manufacturers include Ernie Ball, Martin, GHS, D'Addario, and Elixir, among others. Make sure you have a string winder to make installing the strings go faster, and some pliers with a fine wire cutter to clip the excess string from the tuning post, a well as some guitar polish - changing strings is a good time to perform some routine maintenance. Keep a clean cloth in your case to wipe down the strings after each use, along with extra bridge pins for your acoustic guitar. Regular string changes are the best way to keep your tone crisp and clear, so grab a pack and tune 'em up!
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.
Open tunings improve the intonation of major chords by reducing the error of third intervals in equal temperaments. For example, in the open-G overtones tuning G-G-D-G-B-D, the (G,B) interval is a major third, and of course each successive pair of notes on the G- and B-strings is also a major third; similarly, the open-string minor-third (B,D) induces minor thirds among all the frets of the B-D strings. The thirds of equal temperament have audible deviations from the thirds of just intonation: Equal temperaments is used in modern music because it facilitates music in all keys, while (on a piano and other instruments) just intonation provided better-sounding major-third intervals for only a subset of keys. "Sonny Landreth, Keith Richards and other open-G masters often lower the second string slightly so the major third is in tune with the overtone series. This adjustment dials out the dissonance, and makes those big one-finger major-chords come alive."
Guitars have been played since the Renaissance era, after descending from the ancient Greek instrument, the kithara. Or, at least, that's how the theory goes: the only real proof for this is the similarities between the Greek word and the Spanish word, quitarra. Early guitars often had four strings, evolving into the six-string version we know today in the late 1600s. Anton Stradivari, the famous violin-maker, also had a hand in making guitars. There's now only one Stradivarius guitar left in existence.