Re: Bringing stuff on airplane
As an airline employee I can tell you that airport security ain't going to care about guitar strings. The Rode mic on the other hand is something he may get questioned on and if you really care about it, he should bring it with him as part of his carry on luggage.
Realistically if airport security has a problem with your brother's luggage the airline would probably call him out for questioning. The thing is, putting anything of real value in checked luggage isn't a wise as things DO GO missing when put in regular checked luggage. I've seen people lose laptops, cameras, camcorders, jewelry and other things in checked luggage.