There were no stable orchestras in Madrid’s public theatres during the first half of the Eighteenth Century, and a variable number of instrumentalists were used on each occasion. This paper discusses the development of the two town-owned theatres in the second half of the century, when the orchestra was considered an important element and a new way of hiring musicians developed, based on sources kept at the Archivo de Villa de Madrid, Sección de Secretaría./nRené Andioc and Mireille Coulon in their Cartelera teatral madrileña del siglo XVIII: (1708-1808) refer to the companies that worked in both theatres in the second half of the 18th Century, those of de Josef de Parra, María Hidalgo, José Martínez Gálvez, Juan Ángel, Águeda de la Calle, ...