Sometimes we see questions which seem to be simple requests for external resources. Another variant on this is the request for titles from the literature on some topic.
This is something that I have wondered about before, but I have in mind this question, at the moment. It is an understandable question, and could possibly lead to useful answers, but it also seems that the answers would be primarily opinion-based. Then again, many useful answers to musical questions seem to shade into opinion. Looking again, there is now an answer to this question which looks to contain useful information, and which mentions the first thing that I thought of when I read the question (the books of Jimmy Wyble).
From the help center page about on-topic questions, questions should not be about:
requesting external resources (questions should be specific and answerable on this site; external links are for references and supporting material)
Further, one of the reasons for closure is that a question would require answers which are primarily opinion-based.
Should a question such as the one linked to above be flagged as opinion-based, or for some other reason? Alternatively, given that many useful musical questions necessitate a measure of opinion, should such a question be flagged at all?