Kinga G_yk plays "Tears In Heaven", Jeff Berlin - cover. Four strings and a lower octave, but how many can do this with a six-string?
Fretless Guitar - "Yaram Sõzlar." An arrangement of a turkish folk song called "Yaram Sõzlar A_rõr Ba_õm" for fretless guitar in standard tuning.
Roy Smeck demonstrates the precursors to modern guitar pyrotechnics on a soprano uke, circa 1940s.
Esteban Antonio's "Ha-Shem" is a 17-string Grand Concert Harp Guitar with a bowed section