Harmonic techniques are not limited to the guitar. In fact, classical string instruments are capable of producing these harmonics. To play a harmonic, instead of fingering a note as usual, the performer lightly touches the string with a finger. This causes a high-order harmonic to resonate throughout the string at twice the normal frequency, producing a ghostly tone. An excellent example of the effects that can be achieved may be found in the final movement of Beethoven's string quartet op. 130.