Becoming a big music channel on YouTube is pretty much mission impossible unles you're already famous in real life.Why ? Because you can't use SEO to attract an audience. People search for band names or song titles and if they don't know your band or song, they won't be searching for it. Catch 22.
Honestly if I were a musician and I wanted to make a career out of it, I'd be using YouTube NOT to try to become a big channel (see above), but to help launch my OFFLINE real-life music career. So I'd make a few videos of me playing my music and upload them to YouTube and then I'd be sending out emails with links to my channel to record companies, concert venues, local bars, local media, press etc to try and get my name out there in the music industry itself rather than on YouTube. The goal isn't to get millions of views on Youtube and earn money from adsense, but to launch my real-life music career. Once you've done that, people will then start searching for your band name and they'll find your channel all by themselves.