This category includes works written for performance during religious services or on solemn occasions. Before the baroque period, most sacred choral works were performed ‘a capella’, which means without instrumental or orchestral accompaniment. Subsequently, orchestral accompaniment became the norm. The most common forms of sacred choral music are masses, cantatas and oratorios. Among the most famous sacred choral works are the Requiem Masses of Mozart, Fauré and Verdi.