In Claudio Monteverdi's lifetime, Western art music stood at a crossroads. There were two major types of vocal music at that time: popular songs on mundane themes and music intended to accompany church services. The former group included fairly simple settings for solo voice and madrigals, which set music for two or more independent voice parts. Church music had evolved by the early 16th century into an elaborate polyphony. Josquin Desprez and Giovanni Pierluigi da Palestrina were the foremost composers in this style, in which four or more parts develop musical lines from the tunes to popular and even bawdy songs. Each of the four or more parts wove these tunes together in a dense counterpoint, with no part assigned a primary melodic or harmonic function. The music displayed the consummate skills of their composers, and sounded breathtakingly beautiful when done by a capable choir. However, by the late 16th century, this type of contrapuntal music had become too difficult for most church choirs to sing and most parishioners to understand.

Church music was just one of the things affected by the 17th century movement known as the Counter-Reformation. Church leaders began this movement in response to Protestant challenges that the Catholic Church had grown too preoccupied with secular, decadent luxury and learned complexity, and grown too distant from the common people. The centerpiece of the Counter-Reformation was the Council of Trent which began in 1545. The council extended over three sessions over the course of 20 years, and explored a number of issues in church doctrine and reform. The last Council, which concluded just before Monteverdi's birth, mandated a reform of church music, excising popular melodies from church services, turning away from complicated, learned music, and stressing that the music be designed to make the text intelligible. In the centers of power and education (e.g. Rome's papal chapel), the older style lingered on, but in everyday churches in more remote areas, a new style evolved in its place.

This new style had roots in a separate, secular movement. Around 1580, a group of musical cognoscenti formed a musical academy, or Camerata, at the court of Count Giovanni Bardi in Florence. The Camerata sought to recreate ancient Greek drama. As they understood it, these music dramas had all of their text sung, with a single voice using music to drive the text forward and accompanied by a harmony instrument. This style of text setting, called recitative, became popular because of its dramatic possibilities, and became the basis of this new music drama form called opera.

The idea of using a single melodic voice accompanied by a harmony instrument quickly found its way into sacred music. Lodovico Viadana, a maestro di cappella in the northern Italian town of Mantua, wrote in 1602 of polyphonic masses and motets being performed with parts left out because of a lack of sufficiently skilled choristers. Viadana proposed adapting the recitative style, and wrote sacred music in which a single singer could be accompanied by a keyboard instrument playing chords around a notated bass line. This monodic style, based around what came to be known as the basso continuo, was adopted rapidly by choirmasters and composers alike. At first, this style may have gained popularity because it was so much easier to write, and because it called for fewer skilled musicians. But even the Roman church composers rapidly took up this style, perceiving a new way to lend expressiveness to text passages.

Monteverdi was born in 1567, in the northern town of Cremona, a small town between Milan and Mantua. He studied counterpoint and sacred composition with the maestro di cappella at Cremona's cathedral. Even as a teenager, Monteverdi drew notice for writing music in the more dramatic new styles. In 1591, he became a string player in the Gonzaga court in Mantua, and became director of music (maestro di cappella) ten years later at the age of 34. By this time, Monteverdi had made a name for himself as both composer and writer about music. Monteverdi wrote of an "old style" which he called prima prattica. This was the dense counterpoint of Josquin and Palestrina, where "the music (is) not commanded but commanding, not the servant but the mistress of the words." In his writings, Monteverdi supported a new style, based around basso continuo and recitative, where text took priority over music. Monteverdi termed this modern style the seconda prattica.

Monteverdi proved himself to be more than a theorist, with the creation of two landmark compositions in seconda prattica. His opera based on the Orpheus legend was staged in Mantua in 1607, and incorporated a far more ambitious mix of recitative and aria than the Florentine camerata had originally envisioned. This potent new mix turned opera into a form which would dominate European culture for the next three hundred years. Then in 1610, Monteverdi published a collection of Vesper music settings which applied the same techniques of basso continuo settings of small groups of soloists to church music on a grand scale. The Vespers were accompanied by a six-part Mass setting in the prima prattica style, to demonstrate that he was equally adept in both old and new styles.

Monteverdi dedicated this publication of 1610 to Pope Paul V, no doubt hoping for an appointment in a Roman church. No such offer came, but at the same time, the post of maestro di cappella at St. Mark's Cathedral in Venice fell vacant. Monteverdi demonstrated his skill as composer and music director at an audition in August 1613, and was hired on the spot. He remained in that post, writing pioneering works in opera, madrigal, and sacred format, until his death in Venice in November 1643.