During the short life of this SE, there have been several different lists of what is on and off-topic (which probably isn't unusual for a SE trying to find its identity). So this post is to make a canonical list of what is on-topic as of May 2016. Make each possible topic a separate answer, and upvote or downvote each one based on your own point of view.
Music-related questions that can be answered with some amount of objectivity, even if there isn't a single, provable, correct answer, and even if the questions generate some degree of opinion based on expert experience.
Examples of what I think qualifies here:
This answer is not intended to include questions entirely based on opinions, like: