This is a technique used by classical and flamenco guitar players in
which the first, second, and third fingers of the picking hand play a
continuous repeating pattern on a single note. A famous example of a piece based on this technique is “Recuerdos de la Alhambra,” by Francisco Tarrega (1852-1909).
On other stringed instruments, such as violins, cellos, and so forth, tremolando is a fast repetition by the bow on the same note. It is used to great effect to produce a feeling of tension, mystery, or danger, particularly when performed within a large ensemble. Depending upon the piece, it may be rhythmic or random in nature. Other stringed instruments that may be played
tremolando include the mandolin and Japanese koto.