The most important achievement of the younger Anerio, however, was his "Teatro armonico spirituale" of 1619, which is arguably the first oratorio. It includes the earliest surviving obbligato writing for instruments by the Roman School. Instrumentation is indicated with unusual care, and the alternate instrumental and vocal passages were greatly influential in works of the following decades. Unlike the works of the Venetian school, many of which were essentially grandiose motets, the "Teatro armonico spirituale" was in Italian; it included stories told musically but not acted (as would be done in opera); and voices and instruments alternated movement by movement. The piece included settings of the tale of the Prodigal Son and the Conversion of Saul.