You may have been told that you need to find scholarly or peer-reviewed articles for your research. Scholarly articles are written by experts in a particular field (people like your professors) and are published in specialized journals. These articles are often only available in libraries. Peer-reviewed articles are reviewed by other experts in the same field, who evaluate the research to determine whether it is good enough for publication. 

Scholarly articles are usually written about very specific questions or topics. They aren't as useful if you don't already know much about your topic, although browsing articles that have been published on your topic can give you a sense of how experts are researching and talking about that topic. 

You can find Scholarly Articles in OneSearch, but you may also want to search in some specialized databases dedicated to the performing arts.