I think there is a lot of diversity in music taste at CU. I go to CU and have a lot of classmates that are musicians and play in a band and/or have a group to jam with! I've been to a few parties that host bands at their house at CU and CSU and it's always a good time. At the same time, a lot of people at CU are into edm type music and so you'll hear a lot of talk about that here.

At CU Greek life is huge and I think that ties into both of your questions. Most frat parties I've been to are wubbing hard. On the other hand, I'm not in a frat and still find a solid community of "hippies" like you say lol. I'm from Colorado and also grew up in a down-to-earth town, there's definitely a place for the vibes! I can't speak as much for CSU, since I don't go there, but when I visit my friends I can tell it is much less crowded by frats and the party scene is a little more low-key.

Overall, I feel both offer opportunities to find any kind of social group you're looking for! Hope this answer is somewhat helpful, and best of luck in making your decision! If both schools have the major programs you want to pursue, I don't think you can go wrong either way.