There are a lot of composers. Even if we limit tags to composers who have at least 5 questions, we will probably be facing delicate decisions on naming conventions and tag duplicates.
I would take a wider approach and think in terms of definition of the site. On Music: practice and theory, should there really be a tag about each specific composer?
I'd rather have a [baroque] tag grouping baroque composers than [locatelli],[bach] and/or [tartini] tags.
disclaimer: I come from Stack Overflow, where such questions apply on huge volumes of questions. Maybe all this decisioning [sic] I'm afraid of is not relevant here.
However, I really think we should learn from other sites experiences. On this matter, having many too specific tags is not the way to go because it generates a lot of work from mods and the community to manage tag naming, editing, removal, synonymizing (something like that) etc.