The Reductions were communities in the area of what is now Paraguay, Argentina, and Brazil, populated by local Indians, but governed and administered by members of the Society of Jesus, the Jesuits. The work in this border area between Spanish and Portuguese interests began in 1609AD. Several other important Jesuit missions were also founded in the area of modern Bolivia, and their work will be included here, as well.
These missions in the interior of South America thrived, though not without challenges from certain colonists, until the 18th century expulsion of the Jesuits by both the Portuguese and Spanish crowns. The Portuguese had never liked the project, but the 1767AD expulsion by the "enlightened" King Charles III of Spain was a devastating blow. Still, the remnants of these remarkable missions remain in the stone ruins that are still to be found.
Façade of São Miguel das Missões in the Rio Grande do Sul State of Brazil (#8 on the map above)
The interior of the Jesuit Church of San Xavier in Santa Cruz, Bolivia.
Aside from the obvious architectural achievement of the Jesuits, some rather impressive music was composed by these missionaries and at these missions.
Domenico Zipoli (+1726) was a Tuscan musician who joined the Jesuits in 1716 to come work in the missions. He was an organist and composer in Cordoba, Argentina, until his death. Just recently discovered is this delightful setting of the Mass, Missa San Ignacio. This particular Mass gives you a very good idea of what was popular, and performed, in these missions -- "[o]ne manuscript is dated fifty-eight years after the composer's death 'copied in Potossi 1784.'" The first selection is the Kyrie, the second the Gloria:
The other selection I will offer here is actually a "Jesuit Opera" composed by Zipoli, along with the Swiss Jesuit Martin Schmid (+1772), and "Indios Chiquitanos." Schmid actually worked with the missions in what is now Bolivia. This Opera is about the founder of the Society of Jesus, St. Ignatius of Loyola, hence the name: