The Mutopia Project takes sheet music, that is no longer under copyright, and digitises it making it available for free on the internet.
Period composers in the Mutopia archive
The following list isn't comprehesive and may not be up to date. You should check the Mutopia homepage for music of interest.
- Thoinot Arbeau (1519-1595)
- Adriano Banchieri (c.1567-1634)
- Vincenzo Galilei (1520-1591)
- Luis de Milan (1536-1561)
- Josquin de Pres (c.1440-1521)