AddingtonMitchem468
When a mastering engineer performs mastering on a stereo music track he will normally be making small tweaks to the sound. Mastering has some limitations due to the nature of working with a stereo 2 track L/R mix. The mastering engineer does not have the advantage that a mix engineer does by being able to manipulate the multitrack recording. This is widely understood in the professional music industry. As such the scope of the mastering engineer would normally be to effect small adjustments within the music. These small tweaks can however add up to a fairly large subjective improvement in audio quality. In mastering the engineer needs to be highly confident that the changes he makes are correct as any decisions inevitably affect other aspects of the mix.
For example if you are planning on equalizing a snare drum you will also be equalizing the vocal by default. This is the constant consideration of the mastering engineer. As such it takes many years of experience to judge the right compromise. In recent years with the advent of DIY music at home there is a tendency towards mixes being quite out of balance. A good mastering engineer will offer basic mix tweaks and request a re-submission of the 2 track mixdown. However the mastering engineer is running a small business and as such any work done takes time from his schedule of paid work so this good will should not be abused unduly.
There is sometimes the case for what I would call extreme mastering, extreme in that there may not be an option to get mixes tweaked and remixed. An example would be if the music was produced some years ago and the files for the mix have been lost and this final mix is the only one present. For this the mastering engineer will have to pull out all of his/her skills in trying to restore good mix balance and tone. Extreme mastering is not common however when it is required it can be a rewarding challenge for the mastering studio. There are numerous tools which can help with this procedure. Often these tools will be multiband in nature and these split frequency bands will help the engineer reshape the mix in a useful way.
Such problems that require extreme mastering techniques could be, lots of heavy sub bass on a bass line with a normal sounding kick drum, the challenge would be removing bass without ending up with a weak kick drum. Another issue could be an overly loud snare drum in the mix, this requires reducing the level of a snare drum without overly affecting guitars and vocals. So you can see these are not easy problems to solve. However with time and attention to detail and the right toolset the best result for the track can be realized. So when you mix audio do try and keep back ups of the multitracks you work on. This allows recourse to the mix for tweaking which will always be sonically preferable compared with 2 track master tweaks.
