What can you do to make your mixes work best for the mastering engineer? If you're in doubt, many mastering houses offer a free or low-cost assessment of your CD-R or DAT. This is an excellent method to find out if your mix is in the proper condition for mastering, as well as one good way to see if you like the personal and/or business style of the mastering facility. But there are some guidelines to follow in preparing your mix for mastering...
First of all, a good mix is a good mix. If everything is in proper perspective with good balance, then you're probably ready to go. This is assuming you haven't squashed everything with compression, of course. The same 'trick' for testing your mix that we've all used for years can work well to test a mix that's being finished for mastering: burn a CD and go play it in the car. Drive around and see if you can hear everything at a fairly low volume level. The road and wind noise acts as a filter that's ideal for testing a mix.
Don't compress your whole mix (left and right) if you don't know what you are doing. This bus compression cannot be undone, and is one of the biggest complaints from mastering engineers. You should use little to no compression on the final mix.
In mastering, when you have a great mix, you end up with a great master. However, the real challenge is when you receive lower budget projects and can make them sound like a big budget record, Now that's mastering! At that point, the gear is important, your room is important, but most of all, how you use that gear and that room is crucial.
Take along a CD that sounds good to you, one that has the type of frequency balance that you would like your CD to have. It will give the mastering engineer an idea of what you want your finished CD to sound like, given that it's a similar style of music, and you will have a better idea of the sound character of the speakers at the mastering studio. Mastering studio speakers always seem to sound different from what you're used to, but the mastering engineer knows them intimately.
Try to pay attention to the overall sound and arrangement in order to get your mix as close as you can to what you want to hear. If you're in doubt about compression in your mix, do two versions, one with and one without the compression and send both to the mastering facility. The mastering engineer can NOT mix your record. They do not deal with individual track levels, only frequencies. But if you come in with great sounding tracks, he or she will only make them sound better!