Stem mastering is a different method of mastering audio which traditionally uses the stereo 2 track mixdown files. There is some confusion surrounding stem mastering as it appears to be akin to mixing, however this is not the case. Stem mastering utilizes groups of instruments such as bass, guitars, vocals, drums, synths, brass section etc. The mastering engineer requires these groups of instrumentation to successfully perform stem mastering. Stem mastering allows the engineer extra flexibility when adjustments are being made to the overall sound of the music. the goal is still based on ensuring your music translates as good as is possible to as many sound reproduction systems as possible.
Stem mastering does not rely heavily on automation of levels, adding effects and vocal tuning, this is the remit of the mix down session. The basis of stem mastering is to allow the mastering engineer extra flexibility if needed to improve the mastering end results. Little volume tweaks here and there, characterful processing of certain groups of instruments, warming them up, adding width, punch or specific equalization. Stem mastering can be requested if a client does not have 100pct confidence in their mix down, such issues can be communicated to the mastering engineer and he or she will be able to take these points into consideration when working with the music.
Stereo processing will also feature during a stem mastering session in much the same way as 2 track mastering. Stem mastering is usually a little more costly that stereo mastering as the project will take longer to set up and the extra consideration of more sources also takes extra time. The end results can in many instances be better than 2 track mastering alone.
The distinction is really that mixing is working with multi track recordings, eqing, effecting, balancing, compressing, automating and blending all the sounds together as they were recorded. Stem mastering rarely uses more than 8 stereo stems (instrument groups)per master, whereas a mix down can be many individual tracks and performance takes.
When you prepare your tracks for stem mastering ensure you export as 24 bit .aiff or .wav files. Do not send data compressed file formats such as MP3. Also make sure that you export the files from precisely the same place in the timeline of your workstation so they will synchronize in your mastering engineers DAW. the stems should re-combine to sound very much like your original mixdown. It can sometimes be useful to send the original stereo mix as well as the stems.
If in doubt as to whther your mix down will benefit from stem mastering you could always send your mix for an appraisal to a mastering engineer and see what is suggested. In many instances stereo mastering will be fine.
SafeandSound mastering is a high professional yet low cost online mastering service. This text was written by Barry Gardner the mastering engineer who operates the studio. Visit the website by following this link: online mastering studio