I’m going to echo other posters and say that there’s no need to focus on “pre-law” (which as was said, just advising) or do anything specific in order to later apply for law school. He can major in anything he wants, and still apply to law school, and no major will be more or less helpful. He should pick a major based on what he’s most interested in, and not feel compelled to major in political science, unless that happens to be what he’s most interested in. The courses he’ll take in political science won’t really help with law school, or with law school admissions.
Therefore, you really just need to be considering what schools would be great for clarinet performance, and not really worry about anything else. I don’t have any great recommendations for you there, but that should hopefully make the research much easier.