Encyclopedias are great sources for learning background information about your topic. They usually provide "common knowledge," facts and information that you don't need to cite in your paper, because it is generally understood to be true by other scholars and researchers.
You can find information like names, dates, descriptions of particular types of musical compositions, information about instruments, biographical information, and other historical and factual information.
"In a nutshell: You should not use Wikipedia by itself for any primary research (unless you are writing a paper about Wikipedia)." - from Wikipedia article "Researching with Wikipedia"