This is why current "IP" rights need to swing further towards fair use: so you can do this sort of awesomeness. The kid with the trumpet just played a scale; the real value here was added by the remixer, and I think it's bullshit that legally, that trumpet player could send a DMCA takedown notice for this. To the best of my knowledge, the trumpeter has no such intentions; I'm just making a hypothetical here.
Hopefully this sort of remixing will convince the musicians who don't get it yet that it's important to allow everyone to have fair use rights. Damn this stuff is sweet!