The word, however, has a further use, namely, to play 'divisions' on a viol-da-gamba. This was a favourite accomplishment of gentlemen in the 16th and 17th centuries. Sir Andrew Aguecheek numbered this amongst his attainments, (see Twelfth Night 13, 24); and readers of John Inglesant will remember that 'Mr Inglesant, being pressed to oblige the company, played a descant upon a ground bass in the Italian manner.' Playing a descant on a ground bass meant playing extempore 'divisions' or variations, to the harmony of a 'ground bass' which (with its proper chords) was repeated again and again by the harpsichordist, until the viol player had exhausted his capacity to produce further 'breakings' of the harmony.
In 1665 there was published an instruction book in this art, called Chelys Minuritionum, i.e., the 'Tortoise-shell of Diminutions,' hence (Chelys meaning a lyre, made of a tortoise-shell) 'The Division Viol.' The book is by Christopher Sympson, a Royalist soldier, who was a well-known viol-da-gamba player. The work is in three parts, the third of which is devoted to the method of ordering division on a ground.
To give his own words—
