Most scholarly books and journals in music history and theory follow The Chicago Manual of Style. Although a very comprehensive guide, it is not specialized toward music and, therefore, it does not always cover musical topics thoroughly. Follow Chicago for citations, but then be sure to seek the guides below by Holoman, Wingell, and Cowdery for guidance specific to music research. Other specialized research and writing guidebooks can be found in ML 113, ML 3797, and ML 3880.
When using an online source, check for citation information, including a DOI (digital object identifier) or permalink. Library resources usually include citation formats for copying.
OneSearch uses the quotation mark as a symbol:
JSTOR offers a "Cite this item" link to the right of each item in a list of search results: