As others here, I want you to do well w this movie. I think most of us would concur that some people aren't going to be very happy w you and do what they can to discredit you one way or another. While it's none of my business, I, like others here are just trying to help you watch your back. Copyright law can be an iffy thing. You may have already addressed this, but 1 person(s) can hold the copyright for the words and another for the music. So, while 1 may not have an issue, the other might. I have no idea what tunes you plan on using (and don't need to know), but other considerations may be how hungry they are (e.g., only sold 1 song and are looking for some bucks) or how famous they are (e.g., Beatles or Stones - they probably have lawyers that go after these things all day). What you plan to do may be perfectly fine, and, IMHO it might be good for you to know going in if it is. If there are issues, while you may win in the end, it may save time and $$s down the road. You may already be aware of all of this and have worked all of this out with a copyright attorney. I'll butt out now. Break a leg with your movie!
Thanks. We have the attorneys handling it.