What has being a musician got to do with knowing about copyright law? Now if you'd have said you were a commercial rights or entertainment lawyer then that would have indicated knowledge.
You are obviously talking about both! It's not a difficult basic concept to grasp: If you've used music in your film without permission of the rights holder/s then you've stolen it! Unless you are covered by "fair usage" or you have a licence, you cannot have a showing to distributors (or anyone else) without also stealing the music.
I don't know why you started this thread if you already know that your film is so fantastic that festivals and distributors are going to accept it even though they can't legally distribute or screen it. If you honestly believe what you're saying then you should go right ahead, illegally use whatever music you want and find out for yourself what happens.
G