He received training in music as a choir member as well as at the University of Cremona. He worked as a singer and violist and had some motets published as early as 1582. He also became music director and conductor at various courts until he was appointed music director and conductor at St. Mark's Basilica in Rome.
He composed nine volumes of madrigals in his many years as a composer (over 150 works) and it was in the later volumes of madrigals that he began to include more and more compositions in the new Baroque style of composition. As with any innovator, Monteverdi received his share of criticism as his new style was attacked for being crude and taking license with the traditional composing methods. Monteverdi weathered the criticism and continued to innovate the art of music. He began to compose opera in 1607 with L'Orfeo, based on the Greek tragedy of Orfeus. This is the oldest opera that is still performed with any regularity. Monteverdi wrote for an orchestra of about forty players and was one of the first composers to assign music to specific groups of instruments, although the work wasn't orchestrated in the modern sense and still followed the Renaissance tradition of giving the players a certain amount of freedom in execution. The video below gives an idea of how Monteverdi's orchestra may have sounded as the first few minutes of L'Orfeo are played:
Monteverdi also composed many sacred compositions such as the collection titled Selva morale e spirituale (Moral And Spiritual Forest) that was printed in 1640 and 1641. This collection contains 37 works for various combinations of voices and instruments. Included in this set is one of Monteverdi's most recognized works, his setting of Psalm 111 from the Latin Vulgate (Psalm 112 in the Protestant Bible), known from the first two Latin words of the psalm as Beatus Vir. It is scored for 6 - part choir (2 sopranos, 1 alto, 2 tenors, 1 bass) 2 violins, 3 viols or trombones and continuo. It was composed around 1630. The motet begins with a feeling of rejoicing. The middle section becomes more subdued and dramatic until the rejoicing returns with the opening music of the Beatus vir. The music ends with a beautiful and reverent Amen.
Beatus vir, qui timet Dominum, in mandatis ejus volet nimis.
Praise the Lord. Blessed is the man who fears the Lord, who finds great delight in his commands.
Potens in terra erit semen ejus, generatio rectorum benedicetur.
His children will be mighty in the land; the generation of the upright will be blessed.
Gloria et divitiae in domo ejus, et iustitia ejus manet in saeculum saeculi.
Wealth and riches are in his house, and his righteousness endures forever.
Exortum est in tenebris lumen rectis, misericors et miserator et iustus.
Even in darkness light dawns for the upright, for the gracious and compassionate and righteous man.
Iucundus homo, qui miseretur et commodat, disponet res suas in judicio,
Good will come to him who is generous and lends freely, who conducts his affairs with justice.
quia in aeternum non commovebitur. In memoria aeterna erit iustus,
Surely he will never be shaken; a righteous man will be remembered forever.
ab auditione mala non timebit. Paratum cor ejus, sperare in Domino,
He will have no fear of bad news; his heart is steadfast, trusting in the Lord.
non commovebitur, donec despiciat inimicos suos.
His heart is secure, he will have no fear; in the end he will look in triumph on his foes.
Dispersit dedit pauperibus; justitia ejus manet in saeculum saeculi, cornu ejus exaltabitur in gloria. He has scattered abroad his gifts to the poor, his righteousness endures forever; his horn will be lifted high in honor.
Peccator videbit et irascetur, dentibus suis fremet et tabescet. Desiderium peccatorum peribit.
The wicked man will see and be vexed, he will gnash his teeth and waste away; the longings of the wicked will come to nothing.