A stereotyped accompaniment played on a keyboard instrument with the left hand. The chords of the Alberti Bass are played as arpeggios, or broken chords. Named for Domenico Alberti ca. (1710 - 1740) who used them extensively, they are quite common to the works of Franz Joseph Haydn, Wolfgang Amadeus Mozart, and early Ludwig van Beethoven.
The Alberti Bass pattern uses a three pitch chord with the pattern - lowest pitch - highest pitch - middle pitch - highest pitch. The example shows the pattern of B - G sharp - D - G sharp (lowest pitch - highest pitch - middle pitch - highest pitch). This example is also in triple meter, so the third beat repeats the pattern of the second beat. A duple meter would employ the pattern as described. Alberti Bass refers only to this pattern and not to any arpeggiated pattern or broken chords played in the left hand.
See also arpeggio, broken chord.