It is on unamplified guitar. The guitar itself (including the strings) is also a factor, but varying plucking position and method (pick, nail, flesh etc.) gives

It is on unamplified guitar. The guitar itself (including the strings) is also a factor, but varying plucking position and method (pick, nail, flesh etc.) gives huge variations in tone. These things also affect tone on amplified guitar, though less so as more excessive processing (distortion etc.) is added.