Journals that are provided free of charge to the public are a great benefit in the educational and research discourse due to the fact that they are freely available to all regardless of economic status. In a world in which minority populations tend to have less access to the same resources as majority populations, having access to free resources puts everyone on an even field. Open access also speeds the process through which articles are published, which may be both good and bad.
Sometimes, a speedy process for publishing articles may miss on errors both grammatical and in the content. Researchers can also be spammed by predatory and dubious publishers for content. Costs of publishing shift to both the publisher and the researcher, which could make it hard for some journals to stay viable. You will see some of the journals I highlight have stopped publishing after several years.
I'm going to link several resources here that discuss further issues related to Open Access Journals.
The tab above provides a list of a large number of journals focusing on the panoply of music theory from here in America, to Canada, and some from Europe. There are additional journals on music theory in French, German, Italian and many other languages. The list above is also only for journals available through open access, which means they are freely available to any who have access to the Internet. Payment for the publication of these journals is shifted to the publishers and the researchers instead of the readers. On the left, I discuss the benefits and drawbacks of Open Access journals.
Below are databases that Huntingdon College students and faculty have access to, in order to search additional queries on music theory.