In historical studies a primary source is, broadly speaking, any source of information about a topic that was created at the time being studied.
For example, Beethoven's sketches on Schiller's "Ode to Joy" are a primary source for the 9th symphony; Mahler's letters are a primary source for Mahler biography; reviews written after the first performance of Rite of Spring are primary sources for Stravinsky reception.
Sources created after the fact, usually relying on primary sources, are called secondary sources.
There are several terms you can use in a Subject Heading search that are helpful for identifying potential primary sources in the catalog. If you use the Advanced Search feature of the catalog, you can combine subject terms and keyword searching to narrow down your results.
You can also limit results to the Allen Music Library to further refine your results—but bear in mind there might be useful materials in other libraries, depending on your topic!
Here are some useful subject terms to try:
Florida State University Libraries | 116 Honors Way | Tallahassee, FL 32306 | (850) 644-2706