Standard tuning strings. This is done to simplify fingering. A few guitarists, mostly those using tapping, play without this interval, instead tuning in all fourths; thus on a six-string guitar the top two strings become C and F instead of B and E. Other unusual tunings include all major thirds, all minor thirds, and various other choices. In standard notation, the guitar sounds one octave lower than it is written. This is to avoid switching between treble and bass clef, or using ledger lines or 8vb, since it is very common to play past the 12th fret on the E string (E)
String vibration or, perhaps more easily, by adjusting the machine heads, to obtain the same, or a multiple, of the AC frequency to achieve the same effect. For example, in the case of a guitar, the 6th (lowest pitched) string pressed to the third fret gives a G at 97.999 Hz. A slight adjustment can alter it to 100 Hz, exactly one octave above the alternating current frequency in Europe and most countries in Africa and Asia, 50 Hz. In most countries of the Americas—where the AC frequency is 60 Hz—altering A# on the fifth string, first fret from 116.54 Hz to