The music market is very demanding and the competition is huge. If you want your tracks to compete then it is vitally important that your track can hold its own sonically as well as musically. Have you ever wondered why commercial records sound louder than yours? Or why your tracks just don't sound like a "record"? If your tracks have been recorded and mixed at different times (or even at different studios) then you will end up with massive differences in level and tone. Mastering will create a seamless collection of your music that will sound great on streaming services, radio, TV, in shops and most importantly – in the home of the listener. Whether your music is for commercial release or you are sending demos to get a deal, then you need mastering.
In addition to the sonic differences you will hear with mastering, it is also vitally important that your master is correctly encoded and produced in the correct formats.