This one was hard for me, I watched other tutorials other than the recommended ones for class and still couldn't figure out how to get my SFX to play only when overlapping the trigger box. It would always just play right when I start the level, and then not play again when overlapping the box. Eventually, I tried turning down the falloff distance, so now it isn't even audible when you first get into the level, but it definitely is in there.
If I was making music or sounds for a game, they would be copyrighted by me immediately as they're made by me. If I wanted to trademark them, they'd have to be specific enough to trademark and I could then use them for branding, etc. If I was contracting them out for a third party, I would more than likely be giving them rights to use it anywhere, change it as they see fit, and have the rights to it, but not the exclusive rights... unless that was part of the deal. I would probably want to reserve the right to use my own music anywhere else that I saw fit. This would be impossible if they wanted to trademark them for their own branding purposes, however. I don't really think music would count as a trade secret ever, unless it was so unique and the way it was made was so important that it could be a trade secret.