A woman representing Necessity, seated on a throne supported by the Fates, is flanked by the planets and by Sirens; representing the Harmony of Spheres. Etching by Agostino Carracci after A. Boscoli after B. Buontalenti.

Bardi's "Intermedi" illustrated the power of music. Three of them (nos. 1, 4, and 5) described "musica mundana" or cosmic harmony, and the other three (nos. 2, 3, and 6) "musica humana" or music at the human level: the first of these (represented in the present etching) showed the harmony of the spheres (Dizionario biografico degli italiani, vol. 6, p. 301, s.v. Bardi). In the centre Necessity holds the spindle of the world. Her throne is supported by the three Parcae (Fates). To left and right of the throne are the seven planets and Astraea. Below, twelve Sirens (DeGrazia Bohlin, loc. cit., reporting the interpretation of A. Warburg)