Personally, I believe that by the time students are in middle school, they should be making some of their presentations in a multi-media format, in addition to developing skills in writing the traditional essays and term papers. However, in my classes, I insist that they use music that is public domain or Creative Commons license (that is, available for non-profit use without payment), although they usually originally envision their projects with one of their favorite current hits as the background track.
But if your students are Moby fans, they may be able to do both.
Moby has just begun to offer some of his music at no charge to non-commercial video projects. Just create an account at MobyGratis.com to check it out.