During the Medieval and Renaissance periods, music was predominantly religious and works were composed to be performed as a part of a religious function, most commonly the Catholic mass. Pre-baroque music was almost exclusively vocal music and there were very few instruments existed that composers could write for, but as more instruments were invented, such as the sacbut (ancestor of the trombone), lute (predecessor to the guitar), the viol (shared ancestry with the cello and the violin), and the harpsichord (which preceded the piano as an instrument with keys) composers began to adapt and expand their music to incorporate the newly invented instruments. In the baroque period, composers began to learn how to effectively utilize the instruments for new found purposes, such as dances. Dances such as the sarabande, minuet, gavotte, and the bourse all were invented alongside the improving instruments. Dances were not the only thing expanding however, new genres such as opera and the concerto (a work that is written for a single, or multiple, featured solo instrument(s) that is accompanied by a larger ensemble) emerged from the new possibilities with new instruments. Composers like J.S. Bach wrote complex pieces for the keyboard with his compilation of pieces called The Well-Tempered Clavier. The Well-Tempered Clavier not only expanded the repertoire for the keyboard, but it also demonstrated the tremendous advancements that had been made with the mechanisms that were in the keyboard and which also allowed the keyboard player to play at much greater speeds. Another essential Baroque composer was Antonio Vivaldi. One of Vivaldi's most famous works is The Four Seasons, which is a set of four violin concertos. Finally, Claudio Monteverdi, was an important composer because he made the genre of opera more popular among other composers and audiences alike. The baroque era was significant because it solidified the foundations of the standard harmonic structures that all Western music would be based on.
