Guitar chord in the abstract musical-theory of chords for all instruments. For example, in the guitar (like other stringed instruments but unlike the piano), open-string notes are not fretted and so require less hand-motion. Thus chords that contain open notes are more easily played and hence more frequently played in popular music, such as folk music. Many of the most popular tunings—standard tuning, open tunings, and new standard tuning—are rich in the open notes used by popular chords. Open tunings allow major triads to be played by barring one fret with only one finger, using the finger like a capo. On guitars
Stringed instrument tunings shown with courses separated by bullet characters (•). Pitch: Unless otherwise noted, contemporary western standard pitch (A4 = 440 Hz) and 12-tone equal temperament are assumed. Octaves are given in scientific pitch notation, with Middle C written as "C4". (The 'A' above Middle C would then be written as "A4"; the next higher octave begins on "C5"; the next lower octave on "C3"; etc.) Because stringed instruments are easily re-tuned, the concept of a "standard tuning" is somewhat flexible. Some instruments: Where more than one common tuning exists, the most common is given first and labeled "Standard" or "Standard/common". Other