JSTOR is a database that contains scholarly and academic sources, mostly article sources. It is a much smaller database than ProQuest, but the sources in this database are very rich, especially for humanities-related topics such as music.
If your genre is emerging or not very established, you will not likely find too much in this database. It is always worth a try. You will want to go broad first by entering just one concept.
It is best to start with one concept, then narrow by adding a secondary concept or select a different field to search for more relevant results.
See the images below for how best to search for sources on this assignment: