One of the most common question I get asked is, "Can you mix and master our music?"
The answer is: "Yes, I can definitely mix your music, but I don't do mastering."
"Why is that?", I hear you ask.
Well, there's a few reasons:
1. Mixing and mastering are two separate but equally important aspects of creating a polished, professional sound and both mixing and mastering engineers spend years learning and perfecting their craft. Perhaps this is not the perfect analogy, but think of your song as a photo. The choice of camera, lenses, location, lighting and subject, along with the actual photo shoot are analogous to the recording process. The development of the photo in the dark room would be the mixing phase. Mastering is taking that photo and giving it to someone who is highly skilled with photoshop to put the finishing touches on it!
2. The mastering engineer should always bring a fresh set of ears to the song/project. The mix engineer will likely have spent 8 or more hours listening to each song while mixing it. It's almost impossible to then take that song and master it; you simply don't have the distance and fresh perspective required. It also begs the question, if a mixing engineer offers to master your song and they hear a tonal imbalance as they are mastering, why did they not fix it in mixing stage?
3. Mastering should always be done in a different room to mixing. This is because no matter how much acoustic treatment a room has, it will always have some slight imperfections in frequency response. Having your mix mastered in a different room will highlight any minor frequency issues within the mix and allow the mastering engineer to correct these with EQ.
So, the upshot is this: Always be suspicious of anyone who tells you that they can mix AND master your music. In my mind they obviously do not have a clear understanding of the processes involved.
Anyone can throw a brick-wall limiter on your tracks and make them LOUD, and hey, if that's all you need then I'm happy to do that for you… just please don't call it mastering!