THEORBO [Fr. théorbe, Ger. Theorba, Ital. theorba, Baritone], the large double-necked bass lute much used during the 16th and 17th centuries as general bass in the orchestra. The body of the theorbo was constructed on the same principles as that of the lute but larger, and the same scheme of decoration was followed. The neck, instead of being bent back at an angle to form the head, was straight, having sufficient pegs set in the sides of the head for from 12 to 16 strings tuned in pairs of unisons; on the fingerboards were marked 8 or more frets for semitones. Above this neck was another without frets, curving forwards and slightly to one side to enable the long bass strings, stretched not over but at the side of the neck, to escape the pegs of the shorter strings. These free strings, known as diapason strings (Ger. Begleitseiten) were plucked à vide like those of the lyre, each giving but one note; the number of these strings varied from 8 to 12.