I moved this to the YouTube Chat forum.
If there are any covers played at the concert, I think part of the ticket sales go to royalty payments to the copyright owners. I think this could create issues on YouTube since although they have negotiated a lot of blanket licenses to allow cover songs to be played on their platform, they might not have the blanket licenses for all of the songs played at a concert.
Also, it depends on the artist, but sometimes artists get upset when people film concerts -- they want people to buy tickets and come in person rather than just watch it online.
As for hooking up the audio -- that should be possible, but you'd need some fancy equipment. A regular webcam won't be enough to hook something like that up. A lot of artists like hearing the crowd, and it becomes part of the live experience...so leaving it out entirely for the livestream might make it feel like something is missing from the show...