(It. basso ostinato, ‘obstinate bass’).
Short thematic motif in bass which is constantly repeated with changing harmonies while upper parts proceed and vary. Originated in cantus firmus of choral mus. and became popular in 17th cent., particularly in Eng., as a ground for variations in str. mus. Hence the no. of ‘divisions on a ground’. Examples exist by Byrd, Purcell, Frescobaldi, Carissimi, and Cavalli. See chaconne.