This chapter examines the repertoire for the Basilica of Santa Maria Maggiore, which constitutes the most stylistically varied corpus of all Scarlatti’s Roman sacred music. It ranges from the concertante style with instruments of the Messa per il Santissimo Natale to the archaic character of the processional motets in the stile di cappella. It also includes the scores in stile sollevato such as Caro mea. In his role as coadjutor and maestro di cappella, Scarlatti was thus able to shape his language and compositional choices according to context and liturgical occasion. The Messa per il Santissimo Natale, with its rich vocal and instrumental forces, gave more scope for significant experimentation and variety of combinations, providing the most conspicuous elements of public performance. On the other hand, in the most solemn works, such as the three processional motets, Scarlatti effectively molded his language to a more archaic style.