The Mastering Engineer (M.E.) will listen to all your stereo songs and let you know of any issues that he hears and feels he cannot correct without remixing. If you have any concerns this is the time to speak up.
The M.E. is going to listen to the song as a whole and thru equalization, compression, noise reduction, sound stage manipulation and limiting give you a cohesive great sounding experience. This is not the process to bring the background vocals down in the mix. Typically the M.E. is making fairly small adjustments to bring out the sonic best. In this process the M.E. will also make sure that all the songs have a similar volume and tone.
Once he is done, take your project home and listen to it through all kinds of playback systems and make sure you are happy with what has been done. It’s pretty standard that if there are any minor adjustments to be made these will be done at no additional charge. If you are unsure what mastering can do for your material, most ME’s will master one song for free so you can see what can be done for you.
Before you even start recording, plan on recording at the highest sampling rate that make sense for you. For todays popular styles, 24 bit x 88.2k sampling rate is the way to go. There is no reason to go any higher in sampling rate as you will get diminishing returns based on the type of music and gear most of you will be recording. You need very high quality gear to record at 176.4k or above.
Acoustic material will benefit greatly at the higher sampling rates. Rock-n-roll, not so much. When you mixdown, do not dither or resample your mix files. Leave them for the M.E.. If at all possible do not mix to standard CD audio, 16 x 44.1. And never to an MP3. Do not use buss compression or limiting. You can use these to monitor with, but do not bounce your files with these processes on. Put your hi-res files on a usb stick or on a DVD.
What is your favorite music mastering tip?