Check out the database LexisNexis Academic to search a HUGE collection of newspapers all at once.
If you already have one good book or article, check the bibliography or the footnotes for additional citations. It is not plagiarism to use the same sources as another writer!
The database RIPM has a large collection of digitized music magazines and journals from the 19th and early 20th century. This database is great for finding out about the historical context of a performance.
There are several full-text historical and current newspaper databases listed under News in the Databases tab on the Libraries' homepage.
Contact one of the performing arts librarians and ask for advice. We have loads of tricks up our sleeves.
Drew Barker (email@example.com), Performing Arts Librarian