Managing background music in Vlogs, while Editing in FCP

I have never read about Youtube blocking or raising concerns about ambient music. First step would be to put the microphone as closest to your mouth as possible. The closer to the actual source, the easier is to reduce the background. Defiantly use the voice isolation filter. Secondly, record the background by itself for 30 sec. ( There are programs that you can have the background eliminate the audio all together. Maybe you should look for programs, I don't have any names that I recommend. You can google that) Third, throw a EQ Channel on the audio track, analyze and look what frequency the music is on. Lower those frequency band while raising the Mid ranges where your voice it. This is not going to eliminate the noise, but it will reduce it. Lastly, I am not for copywriter infringement. Absolulty all artist should be paid for their work, but for what you are talking about, I don't think the copy write police are going to come after you. The most that will happen is you will get an email to stop doing that. The most important thing for isolating your voice is getting the microphone closes to your mouth. the the filters can do their work.

Most music playing in the background is likely copyrighted. Recording at a loud volume and uploading it to social media is a copyright infringement.

You have to carefully choose your shooting location. A good solution is to use a lavalier microphone to clearly record your voice.