If youtube is removing the background music of your videos there is an easy way to fix it. All you have to do is to
Step 1: Make a back up copy of the music file to your desktop or any folder you like.
Step 2: Right Click the file and press properties
Step 3: Click Summary and click advanced. Change everything from music to origin.
after this you can already insert the audio file to your video. youtube wont remove it because it cannot identify the correct details of the file.
hope this helps. ive been doing this for about 2 years already