The only 'legal' way is to subscribe to Youtube Red. It also eliminates all commercials and gives you access to some original content.
A better deal is to sign up for Google Play Music. This is a subscription music service that gives you access to almost all music, on demand on the web or via an App. When you do this they throw in YouTube Red for free. The kicker is the price for Google Play Music is the same as YouTube Red, so the music is 'free'.
In addition, I believe they are still running a 4 month free trial period for this. Try the link on this page.
https://www.dealnews.com/Google-Play-Music-Unlimited-4-Month-Trial-free-for-new-customers/2099263.html