There are many lyrics videos and other audio visualizer videos using songs they clearly don't have ownership own. Many of these receive a copyright strike on Youtube and are subsequently taken down, but many also do not.
Additionally, there are many songs on Youtube in which you will get the message "The copyright claimant allows their content on Youtube and you cannot monetize it" and be allowed to keep the video up.
Also, I don't think I need to mention the number of "streaming" services and song services of websites which are not taken down. So I have two questions:
How do you know if the copyright claimant or owner of them material you are using is allowing their content on Youtube and does fair use automatically cover you for anything related to this (as long as you add some "value" such as an audio visualizer or lyrics)?
Is it illegal to share the music experience of a legally purchased MP3 (play it on your website but do not provide an option for users to download it) or to provide services that play songs (but not download) but are not hosted by your website (in which case you just act as a pointer to other sites which are participating in illegal activities)? What rights/privileges can cover you if you wish to participate in this? I've heard (rumours probably with no legal standing), that as long as you are not monetizing their material, you will not have any legal action taken against you.