I just paid for licenses for some more songs that are on my site.  I license them as cover songs even though I am building instrumentals. I use https://www.easysong.com They offer other services as well but I find their licensing service very helpful and its not as expensive as you would think. I tried doing it myself but it can be very time consuming to find out who owns the publishing rights to a song. First you have to figure out who the songwriter is. Then some songs have multiple songwriters and they will each have their own publishers or it could be administered by a 3rd party like Harry Fox. I'd rather just leave it to the pro's and concentrate on the music