If you work in any kind of editing, whether it's music or video editing, then you will need from time to time to find music without royalties, unless you are willing to pay a fee to use it in your creation. When someone makes a music track this is their intellectual property, that means that it is automatically copyright and no one else can make money from it without their consent and without sharing the royalties. This is a fair law as it means that if you've created something, only you can stand to make money from it – and you wouldn't very well want to make a new music track only to find that someone else is using it on their advert or on a video without your permission – just as you wouldn't want to find someone using a picture of you without your consent to promote something you don't agree with. It's robbing you out of money and it's suggesting your affiliation in something that you had no part in.
However, this does make life more difficult for some other artists whose creations require some element of collaboration and who need certain musical input that they can't create themselves. For instance if you are a DJ and you enjoy remixing music, then you could very well want to use sound bites from singers of them singing. Preferably this would be acapella so that you wouldn't have to edit out lots of background noise (acapella meaning a solo singer or singers with no music instruments providing backing for those who aren't familiar with the term).
Acapellas for remixing then are highly useful in this scenario as they enable you to add small vocal lines to your tracks without having to sing them yourself or edit them particularly. Of course though, getting acapellas for remixing is the tricky part in light of the laws we've already discussed – you can't just go and take non royalty-free vocals from well known songs as you wouldn't have the author's permission to use them.
Fortunately there are some remix sources online where you can download acapellas for remixing and these come royalty-free meaning that you are free to use them in your tracks without needing to track down the musician and pay them lots of money. This then gives you a library of samples to work with that can make your tracks much more melodic.
Another scenario where the royalties on music tracks can make life difficult for artists is on YouTube. Here we were once able to upload any videos with any music track on top, but then the record labels started to notice this presumably and the owners of YouTube (Google) have thus had to put restrictions on which tracks you can use. This leaves you with the option to select a track from a limited selection on the site, much of which is frankly very poor, or to learn to remix your own music so that you can use it on the videos. This makes them more creative and personal and avoids legal difficulties, so it's a great reason to learn to remix and to search for royalty-free acapellas for remixing.