A standard Afro-Latin instrumental ensemble that consists of a rhythm section, two or more horns and vocals (often sung in call-and-response fashion). Tres player and bandleader Arsenio Rodríguez (d. 1970) and his Conjunto Casino enjoy much of the credit for innovating this ensemble form in the 1940s. Before then, the septeto was the standard format for son performance. Rodríguez added the conga, the piano and the second trumpet to create the conjunto, and formalized the instrumental parts: horns played precomposed parts and the rhythm section played repeating ostinato patterns. These innovations not only marked the birth of a new type of instrumental ensemble, but laid the musical brickwork upon which salsa genres developed in New York City.