You would need a license for any songs you upload that are not entirely your original work.
Anything that is written or recorded is automatically protected by copyright. Neither registration nor notification is not required for protection.
As of 2013, the best website where you can download all of the no copyright sounds songs is called YouTube.
No. The YouTube site is property of Google; copyright details of the user-provided content differs from video to video.
It is illegal to download YouTube songs that have a copyright or license. This is true of most songs on YouTube. Some of the artists don't care because it is free promotion and helps them sell songs. You can buy songs on iTunes or listen to some for free.
Unless the songs from iTunes are you own work or you own the copyrights you will not be allowed to put them on YouTube. The advice from YouTube says: Posting copyright-infringing content can lead to the termination of your account, and possibly monetary damages if a copyright owner decides to take legal action (this is serious-you can get sued!).
YouTube is not designed for remixing songs with its video editor. It is best to do song editing for videos before uploading the video onto YouTube. Computer programs like Apple's Garageband can be used instead for remixing songs. Copyright laws should also be taken into consideration when remixing songs.
No, or, more accurately, the fact that it's on YouTube does not affect the legality one way or the other. It is illegal to download a song in violation of its copyright; where you get it is beside the point. So there are some songs that it's illegal to download from YouTube (or anywhere else with the exception of authorized stores you purchase the songs from), and songs that it's legal to download from YouTube (or anywhere else) because they're not copyrighted or because the copyright owner has chosen to allow it.
Absoulutley NOT! Youtube prohibits Copyright. Any Video submitted with music is instantly banned from Monitizing. BUT the video may still be able if they do an appeal on it which the Copyright company will review.
Ostensibly you would know which song is not your own original work.
Some people use Itunes or other ways of buying songs for it.
YouTube and copyright owners decide what content appears on YouTube. YouTube decides based on the community guidelines while copyright owners decide based on copyright laws.
YouTube has an excellent discussion of copyright on their website; see the link below.