Where to get NON-Copyright Music?

In my experience, I use www.freesound.org, although, if the artists choose to license it in certain ways, you will have to give them permission in each video with the music. But you are in a very musician-rich forum. Maybe ask around to see if someone can make you some music?

everything on this planet is going to have some restriction. If you want to do it right which god I want to poke my eyes out on this forum right now use music which grants permission for reuse.

if you want to monetize your video use music in this list that allows for commercial reuse
if you dont want to monetize pretty much everything there is fair game

You can also learn to make your own background music using garaband or something.

for sounds for your videos if you want to add a sound there are huge repositories for this
the two I use are www.soundbible.com and www.freesound.org

again check the licenses before using them but for the most part you can use them.

when you use this stuff take notes. At the end of the video put the information in the credits. Provide a link back to those requiring you give them credit in your youtube page as well.
The rockstar of royalty free composers Kevin MacLeod provides music with an open donation at Incompetech.com -- Make sure to donate generously since he's done so much work and asked for so little in return. The attached video wouldn't be possible without the synthesized stylings of MacLeod. Make sure to give credit in your videos to the artists that made your work possible.
SoundCloud producers will often collaborate with a YouTube producer to promote their audio tracks, if you hear something that you love, contact them with a trade of services request.