guitars have two strings which share tension through
a "head" that pivots under the control of a long whammy
arm. This configuration causes one string to tighten
as the other is loosened, creating a tonal center.
difference of the strings at rest (equal tension) is
an octave, because of the string diameter.
Guitars also have a movable bridge that acts as a big
fret for "hammer-on" and other techniques more specific
to the instrument.
Pickups are mounted under both ends
of the string, allowing for multiple independant string
segments. The range of the string tension is two to
three octaves. The movable bridge futher divides the
string into intervals.
Be sure to visit Neil Feather's website for more info
on former guitars, as well as his many other unique,
innovative and visionary sound creations, projects and
inventions at: www.neilfeather.org