A very popular example of Classical accompaniment based on
triads is the Alberti bass, initially developed by Domenico Alberti
(1710-1740).
Alberti bass is a kind of broken chord/triad or arpeggiated
accompaniment, where the notes of the chord are presented in the
order lowest, highest, middle, highest. For example, if a C major
chord was being played in root position, the order would be
C-G-E-G.