Mastering are usually done on stereo tracks of the songs of an album. The goal is to make all songs the same levels and sounding similar so you are not force to go on the listening device to change EQ or Volume, from track to track and from other commercial CDs

Many softwares exist to do so and most have a mastering guide. The guide of Izotope Ozone is very helpfull to beginners. You don't need to purchase Ozone to read it, it's free : http://downloads.izotope.com/guides/iZotopeMasteringGuide_MasteringWithOzone.pdf

So how come when mastering studios contact me to master my clients tracks they ask for everything individually? And when I get the finished version back it sounds amazing!

Just a guess but they are also remixing your work and adding tricks. This is exactly what I do.
http://recording.org/threads/recording-drums-under-less-than-ideal-situations-please-help.55232/

Then, continue to master it.

Some mastering centre ask for 3 mix, what you think is right. +3db vocal and -3db vocal

[[url=http://[/URL]="http://www.amazon.c…"]Mastering Audio: The Art and the Science: Bob Katz: 9780240808376: Amazon.com: Books[/]="http://www.amazon.c…"]Mastering Audio: The Art and the Science: Bob Katz: 9780240808376: Amazon.com: Books[/]

the book is a bit heavy at times, but worth a few reads.

ChrisChase, post: 409021 wrote: So how come when mastering studios contact me to master my clients tracks they ask for everything individually? And when I get the finished version back it sounds amazing!

Mastering studios always need one WAV file without any processing on the master fader and if there's any you should write down what you've used to help them out.
If they ask individual tracks well that's mixing and not mastering :)

Paschalis I., post: 409127 wrote: Mastering studios always need one WAV file without any processing on the master fader and if there's any you should write down what you've used to help them out.
If they ask individual tracks well that's mixing and not mastering :)

true but and also worth mentioning:

I will often take an existing master and recook it.

I mean, It might not taste like the best steak had it been cooked to spec without sending it back but, some stuff under done, even years back like on say DA 88, DAT tape/ previously mastered, I'll run it through my system and it comes out sounding pretty improved.

first if you have to ask where to start when you master, you probably shouldn't be trying to do it.

mastering was the art of transcribing recordings from tape to vinyl. when cds came int vogue many mastering engineers switched to burning cds from tape or daw mix files and they included "track sweetening" as part of the service. this is what is called mastering now days.

if a mastering house wants all of the raw tracks then that's they’re way of being polite. what that really means is your mix sucks and they need to completely remix the project to acceptable levels. some houses will request stems to add a little more of one element or another. while not as bad as the "your mix sucks" scenario, it's still not a good thing. if either of these things are happening to you often, again you probably shouldn’t be attempting to master your own tracks.

As Kurt mentioned, if you are providing someone with all of your tracks, then it is being remixed.

Mastering is - and this is a simple definition because I'm pretty sure you don't know the difference so I'll keep it basic - the process of taking a finished 2 mix and adjusting volume and tone to each whole finished mix/song so that there is a fluidity, tonal similarity and volume continuity from song to song on an album/record/CD... there's more to it than that but again I'm keeping it simple for your sake at this time.

If you are sending individual tracks, then they are mixing, which involves taking all your individual tracks and mixing them together into a finished product using various processors, effects, EQ, volume level adjustments, etc..

If you are sending them a final stereo mix ( 2 mix) you did yourself, then they are mastering.