The main problem with rock bands is not participating in the band but avoiding the problematic lifestyle often associated with it. If you are strong enough in your faith to avoid the immoral situations that may be part and parcel with performing onstage, playing in clubs, and perhaps, if you become successful, touring, then there is nothing intrinsically sinful about playing music and singing with non-Catholics.
In your case, as you will be responsible for the lyrics, you, as a Catholic, will not write songs that glorify immorality. Were someone else to consider joining a band and he were not responsible for the lyrics, he would have to consider more carefully if his (name removed by moderator)ut in the music were influential enough to prevent being expected to participate in performing morally problematic songs.
