"With a note of music, one strikes the fundamental, and, in addition to the root note, other notes are generated: these are the harmonic series.... As one fundamental note contains within it other notes in the octave, two fundamentals produce a remarkable array of harmonics, and the number of possible combinations between all the notes increases phenomenally. With a triad, affairs stand a good chance of getting severely out of hand."
Electric guitars and bass guitars have to be used with a guitar amplifier and loudspeaker or a bass amplifier and speaker, respectively, in order to make enough sound to be heard by the performer and audience. Electric guitars and bass guitars almost always use magnetic pickups, which generate an electric signal when the musician plucks, strums or otherwise plays the instrument. The amplifier and speaker strengthen this signal using a power amplifier and a loudspeaker. Acoustic guitars that are equipped with a piezoelectric pickup or microphone can also be plugged into an instrument amplifier, acoustic guitar amp or PA system to make them louder. With electric guitar and bass, the amplifier and speaker are not just used to make the instrument louder; by adjusting the equalizer controls, the preamplifier, and any onboard effects units (reverb, distortion/overdrive, etc.) the player can also modify the tone (aka timbre or "colour") and sound of the instrument. Acoustic guitar players can also use the amp to change the sound of their instrument, but in general, acoustic guitar amps are used to make the natural acoustic sound of the instrument louder without changing its sound that much.
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!
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.