I know the general changes of music in the Renaissance, but when exactly in the Renaissance did the changes such as more melody and longer pieces start?

Read carefully and take good notes.

http://www.medieval.org/emfaq/beginlst/nocds.html

http://en.wikipedia.org/wiki/Renaissance_music

Let us know what you decide.

To determine when the changes in music during the Renaissance, such as an increased focus on melody and longer compositions, began, you can follow these steps:

1. Understand the Renaissance period: The Renaissance era spanned roughly from the 14th to the 17th century, starting in Italy and gradually spreading throughout Europe. It is characterized by a renewed interest in art, literature, and music, with a focus on humanism and the rebirth of classical ideas.

2. Identify the early Renaissance: The early Renaissance in music is generally considered to have started around the mid-15th century. During this time, there was a gradual shift from the modal system of the medieval period to a more tonal system. Composers like Guillaume Dufay and Johannes Ockeghem made significant contributions to this transitional period.

3. Explore the works of Josquin des Prez: Josquin des Prez, a composer of the late 15th and early 16th centuries, is often acknowledged as a pivotal figure in the development of Renaissance music. He introduced a more individualistic style with expressive melodies and sophisticated polyphonic structures. His compositions, such as "Ave Maria... virgo serena" and "Missa Pange lingua," exemplify the evolving trends of the era.

4. Consider the mid to late Renaissance: By the mid-16th century, composers such as Giovanni Pierluigi da Palestrina, Orlando di Lasso, and Thomas Tallis were producing longer choral compositions that focused on intricate polyphony and elaborate melodies. Palestrina's Masses and motets, for example, are renowned for their melodiousness and contrapuntal complexity.

In summary, the changes in music during the Renaissance, including an emphasis on melody and longer compositions, started around the mid-15th century with the early Renaissance period. However, the full realization of these changes can be observed more prominently in the works of composers like Josquin des Prez in the late 15th and early 16th centuries, as well as in the later works of composers from the mid to late Renaissance period.