Stem mastering

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Whilst mastering is a very distinct process it seems there is no end to it's presence immediately after the word "mixing" on the Internet. "mixing and mastering" seem to almost go hand in hand with each other when reading audio production forums. Another term that is used is "stem mastering" this process will be explained later. However mastering is a very distinct procedure compared with mixing (as is stem mastering) and we will analyze the differences between the two and also throw in some information regarding stem mastering. It seems there are quite a lot of people who find it confusing as to what mastering is actually capable of achieving with their music productions. Mastering is the final process in the production chain. Mixing is where the multi track recordings (or drum machines/synths etc.) are balanced against each other on a mixing console or within a digital audio work station. Great attention to musical balance is paid using faders to balance the audio, often automated. Controlling the dynamics and tone of the music tracks by using compression, gates and equalization is also the mainstay of mix down. In addition effects processors are used to add reverb, delay, chorus etc. Not every mix is perfect and some have less than ideal overall balance. Some mixes are presented that do not quite have the right balance of instrumentation. In many instances the mix is very good and there is no need for the client to request feedback. Here are some common problems in a music mix. 

Kick drum too loud, snare drum too quiet, lead vocal too loud or quiet, backing vocals too loud or quiet, very harsh sounding guitars, bass guitar making clicking noises as the strings hit pick ups, vocal pops, harsh sounding hi hats, bass guitar too low in the mix, kick drum has too much sub bass frequencies. Such issues as these are often best dealt with in the mixing stage but are sometimes only discovered during mastering when the music is heard on very high resolution monitoring equipment. You require full range monitors and good acoustics to hear what is really present in the mix.You need to be able to trust your mastering engineer and hope that he or she can give feedback regarding such mix issues. Whilst mastering a track the engineer can often try and resolve these problems but it is normally a compromise as the mastering engineer is working with the stereo 2 track mix and not the individual multi track files. 

Of course this makes it difficult to fully isolate any given instrument or sound in a stereo 2 track file and process it accordingly. In this case it is great if the mastering engineer has had prior mixing experience in his audio engineering career as he will instantly recognize the problems and be able to advise the best way to resolve the issue in the mix. This means less compromise overall and better end results. Stem mastering is also an option, more about this process later. I have found producers, musicians and record labels very much appreciate this feedback regarding their music and releases and it is great for both the band and the mastering studio as the music sounds better and reflects on both parties in a favourable light. When you select your online mastering studios it is important to make sure that you check that your mastering engineer has the experience required to be up to the task. 

If the engineer has had recording and mixing experience he will understand mis balance and be able to give good advice to you at the mastering stage if you request it. Mix feedback or appraisal is an important aspect of mastering these days especially for enthusiastic young musicians and more inexperienced bands who are finding their way and improving their playing and production skills. Mix feedback is usually only given if it is requested. An exception would be if there is a severe technical issue or very out of balance mix that would be difficult to master as is. The tools that are available for mastering audio are no doubt very sophisticated. As such in mastering it is possible to do the following tasks. 

1)Removing troublesome and problematic resonances for playback systems. 

2)Increasing the level (perceived) and also reducing, entire mixes. 

3)Removing pops/glitches and clicks and other audio oddities.

4)Adjust the tone of a mix, this could encompass adding/removing bass, brightening, enhancing presence, adding warmth, reducing harshness. 

5)Enhancement of the stereo image and widening / collapsing if need be. 
"What is audio mastering?" fact : Stereo mastering cannot address more severe issues of mix balance.Rarely can issues of balance exceeding 1 - 2 dB be rectified in a satisfactory manner, so ensure your mix is well balanced before sending to online mastering.Stem mastering can offer increased flexibility for the mastering engineer.

This list is not complete but gives and idea of the possibilities of work a mastering engineer can achieve with the right tools and abilities. 

Another form of mastering technique is stem mastering. Stem mastering requires groups of musical instruments to be exported from the digital audio workstation.Stem mastering gives the mastering engineer considerably more flexibility to produce a better master. Stem mastering is usually discussed when there are mix problems that have yet to be resolved. Stem mastering is a relatively small percentage of mastering work that is undertaken in professional mastering studios. In saying this some clients like the control and flexibility this give the mastering engineer as they trust the engineers ability to process stems and create a better master. In some instances it can achieve better results than with a stereo file. In essence you are creating and delivering files of the groups of instruments that create the mixdown. These might be bass, drums, horn section, backing vocals, lead vocal, synthesizers etc. etc. Each stem must be exported from exactly the same point in the DAW so that they synchronize in the mastering engineer's digital audio workstation. In addition consideration must be made as to whether to export stereo or mono stems. Any group that has panning within it or stereo sources must be bounced as stereo interleaved. A bass guitar may be mono. But in any event pay attention to the stereo image before bouncing the stem and make the right choice. Stem mastering is invariably more expensive than stereo 2 track mastering. This is because of the extra time to set up the project and often there is more to consider when the stems are available for tweaking, even if in the end they do not get adjusted.
This explanation is of course quite general and every mix that a mastering engineer receives will have a different set of sonic characteristics. Mastering is normally a combination of identifying tangible sonic/technical problems and subjective enhancement of the music. The mastering engineer will perform this whilst constantly considering if the subjective improvements outweigh any detrimental effects of the processing.It is fair to say that this is where the skill and focus of the mastering engineer is paramount. 
©Copyright 2011 Barry Gardner
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