Example: Woodstock (1969)
1) Grove: see the article on Festival for historical context. Festivals are listed by Country at the end of the article in part 7. "List".
2) Check Music and non-music periodicals (In the drop down menu select either contemporary or historical) indexes: Current or Historical Find databases such as Rock's Back Pages, and Rolling Stone Archive.

3)Check the Vassar Library Search Online Catalog for a variety of sources: Woodstock 1969

4) Wikipedia: Woodstock Use Wikipedia articles with caution, BUT get ideas from it for references and external links.
5) Get more information by searching the above sources for the names of artists who were involved, their websites, venue sites, etc.