William Byrd was a composer during the English Renaissance. He wrote a variety of types of church and secular music, keyboard, and consort music. For many years, scholars knew little about his birth, upbringing, and education. However, in the late 1990s, researcher John Harley discovered documents that gave Byrd's age in 1598 as "58 years or ther abouts."

He was born in London, the son of a Thomas Byrd, about whom little is known. He had two brothers, Symond and John. He also had four sisters. He was a pupil of the composer Thomas Tallis, who was the leading composer of his day. Byrd began composing when he was a teenager, predominantly sacred music, including a alternatim psalm in the Sarum liturgy, which was favored by Catholics. Therefore, it may be assumed that Byrd wrote the piece during the reign of Catholic Queen Mary.

Byrd may have been a choirboy in the Chapel Royal. His first employment as a professional musician was as organist and choirmaster of Lincoln Cathedral. He remained there for nine years, and while overall the experience was happy and successful, he was cited by the Dean for "certain matters alleged against him," and for a time his salary was suspended. It is possible that the charges were related to writing and performing overly-ornamented pieces. In 1568 he married Julian Birley. It was a long, apparently happy marriage that produced at least seven children.

During the years that followed his marriage, he became very productive, composing much of his most important work. In 1575 he received a particularly special honor, shared with his former instructor, Thomas Tallis. The two composers were granted a patent for printing and publishing music. They were the only two composers in England to have the right to do so, and they were the only two composers in the kingdom who were allowed to use the paper specially meant for the printing of music.

By the mid 1570s, Byrd became increasingly interested in Catholicism. While he was raised a Protestant, he began associating mostly with Catholics and his wife was charged at one point with not attending Anglican services. This was a great risk to take during the 1570s and 1580s. Pope Pius V's Papal Bull, devised in 1570, absolved Queen Elizabeth I's from allegiance to her, which for all intents and purposes made her an outlaw in the eyes of the Catholic Church. Thus, Tudor authorities were ever more vigilant in seeking and discovering secret Catholics.

Despite the risks, Byrd continued to write a variety of music, including much sacred music that was heavily-tinged with Catholicism. By the 1590s he was composing masses, but he continued to write Anglican-appropriate music as well. It was perhaps his great versatility in accommodating a given climate of the times, and the overall appreciation and popularity of his music that saved him from typical Tudor punishments.