List of extended-range guitar players

While the six string guitar has been more or less the standard instrument since the mid-19th century, guitarists and luthiers have experimented with additional strings to extend the range of the instrument practically since the emergence of the modern guitar form, sometime in the 15th century. Seven, eight, nine, ten and more strings have been used by guitarists seeking to increase the range of pitches available from the instrument.

Source: Wikipedia — List of extended-range guitar players (CC BY-SA 4.0)