Sebastián Aguilera de Heredia was a Renaissance-era Spanish composer whose substantial output of vocal and organ works was devoted strictly to church usage. He is perhaps best known for his 36 choral settings of the Magnificat, found in his Canticum Beatissimae Virginis deiparae Mariae (published in 1618). Much of his organ music was important, as well: many consider Aguilera a seminal figure in the development of the Aragonese school of organ music. Aguilera was born in Zaragosa, Spain, probably in mid-August 1561. Virtually nothing is known of his childhood and early teen years, though it is believed he studied music in his native city with Juan Oriz and Melchor Robledo. He also prepared for the priesthood during his formative years and was ordained in January 1584 at Saint Paul the Apostle Church, in Zaragosa. The following year he secured the prestigious post of organist at the Huesca Cathedral, where he would serve until 1603. Probably his earliest compositions date to his Huesca period. On September 29, 1603, Aguilera assumed the post where he would spend the remainder of his career -- chief organist at the La Seo Cathedral in Zaragosa. Naturally, his role there also encompassed performances of priestly functions, but it was here, too, that he composed his most famous compositions, like the aforementioned collection of Magnificats, whose 1618 publication would garner him substantial bequests from both the La Seo and Huesca Cathedrals. Aguilera had also become an expert in organ building and maintenance during his career, his first major undertaking in this rare craft coming when he served as manager of construction of the organ at the Huesca Cathedral in 1588. At the La Seo Cathedral he regularly supervised repairs and renovations to the organ. By the early 1620s, Aguilera had become a powerful figure in Spain, both musically and in church matters. His music, though not always innovative, influenced the works of younger-generation figures like Correa de Arrauxo, Jose Cabanilles, Rodrigues Coelho, and José Ximénez. Ximénez, probably his most important student, was appointed his assistant at the La Seo Cathedral in 1620, owing mainly to Aguilera's considerable sway there. Aguilera died in 1627. His protégée Ximénez, in accordance with Aguilera's wishes, succeeded him as first organist at the La Seo Cathedral. Aguilera is generally regarded as the most important Spanish composer of church music from his generation.