MIDAS Tip-Sheet 7: CD Mastering

Mastering is a process which takes place after all the tracks for your CD are recorded and mixed. There are some myths and misunderstandings about mastering, so here we will look at some of the basics of what you need to know.

The main purposes of mastering are:

To compile the running order of tracks;
To adjust sonic frequencies and remove unwanted noise;
To adjust volume levels of tracks relative to each other;
To add PQ encoding, the electronic data needed to reproduce CDs with the correct track numbers and spaces.

ISRC codes (codes which electronically log artist copyright and publisher information from radio play) can also be added at the mastering stage if needed.

What mastering cannot do is make a poor mix sound perfect, so the logical approach is to get the recording and mixing right and treat mastering as fine tuning. A mix should be as close to the real thing as you can get, and mastering will give it the extra warmth and sparkle you hear on commercial releases.

Mastering is a specialist skill, and though it may be a slightly different ball game from the days of vinyl, the principles are the same and it requires a great deal of experience and expensive kit. It can therefore be a costly process for the customer at anything upwards of £50 per hour, but if your mixes are in good shape, a five track EP can be turned around in about four hours, maybe less on a good day. If your mixes are on CD they can be loaded up in a matter of a few minutes, if they are on DAT they will have to be played into the system in real time.

When all your tracks are loaded in, the engineer will arrange them in the running order you want and then analyse each track to see what needs done. The most common situation is that, overall, your mixes may be a bit dull or lacking in top end (this might be to do with what speakers you mixed on) or the bass end is too heavy (perhaps due to the characteristics of a home studio set up). These issues can be easily corrected. More specifically, attention to mid range frequencies can enhance the presence of vocals or guitars, and the engineer can look at any phasing problems with stereo effects or widely panned keyboard sounds. Some common problems, such as electrical earth hum or digital noise, can be eliminated or at least reduced, but as we suggested earlier, the best idea is to eliminate it at source during recording just in case.

You will see each track on the system represented as a wave form, and you may notice that some tracks are higher in overall level than others. The mastering engineer can rectify this and achieve consistency across all the tracks, both visually and by listening closely (don’t underestimate the human ear!).

An important point to consider here is whether you want maximum loudness within each track or if you want your music to have some natural dynamics. Put one of your favourite CDs on a player and look at the level meter while it plays. If the meter is constantly at 0db throughout, then the track has been maximised. If it rises and falls during play then the track has been mastered to preserve some natural sounding dynamics. Maximising tracks is really all about making a track sound as loud as possible and in theory (but not in practice) louder than everyone else’s. This generally involves applying a little bit of distortion and is a judgement call, but bearing in mind all major radio stations compress their broadcast signal to a degree anyway, you could argue a little natural feel is more musical and representative of the music you created. Discuss it with the engineer and their experience will guide you along the right path.

When all this has been done and any unwanted squeaks and bumps have been removed, the engineer will produce a master CD for you, along with a reference copy which you must take home and listen to. The studio will keep your session for a period of time until you are satisfied with it (though they will charge you for any subsequent changes to anything you agreed at the time of the session). You may have changed the running order of the tracks during the mastering session, so make sure you keep a note of the final running order for your artwork.

You will then send the master copy to the manufacturer, and this will contain all the electronic data for pressing.

Why should you have your tracks mastered?

If you intend to reproduce your CD in any quantity via a pressing company, the very least you will need is PQ encoding (this stands for Pause and Quiet, the means by which a CD player detects the spaces between tracks). Some duplication companies will provide this service at a one off cost avoiding the need for you to go to a studio, but bear in mind this won’t alter the sound of your mixes. This is probably adequate for demos if you are reasonably happy with the mixes.

You would most certainly want a more in depth mastering session for a commercial release, especially one that may get radio play. Mastering engineers will know how to get the best out of your mixes with that in mind. As it is most likely your tracks will have been recorded on a digital system, they may run your mixes through an analogue desk or valve compressors to add some overall “warmth” and presence.

A third reason, and one not to overlook, is that mastering can give you some additional confidence in your CD, as it will have been given some extra care and attention by an experienced engineer. At least you will know you have done everything possible to maximise the potential of the product and any undetected frequency problems have been ironed out.

Again, if you don’t like your mixes don’t waste money on mastering. If your mixes are all wrong, just go back and re-mix. Final mixes should sound good, just maybe lacking the punch or brightness of some commercially released CDs in your collection. Mastering will get you as close as possible to that.

Booking your session

There are several mastering studios in Scotland. Shopping around and personal recommendation will help you decide which is best for you.

When booking your session, explain what your project is and what you hope to achieve at the end of it (number of tracks, where it was recorded and whether it is for commercial release). Get a price per hour (including VAT) and ask if there are additional costs for CD reference copies. If you have any specific technical questions, ask to speak to an engineer.

It is difficult to be specific about how long a session you will need. Some mixes need very little adjustment, others need finely balanced. As a general guide:

Single (3 tracks): 3 hours

EP (five tracks): 3-4 hours

Album (12 tracks): 4-5 hours

Bear in mind, each session includes at least one full playback, so for an album that could be anything up to 70 minutes. A studio shouldn’t charge you for hours you don’t use, but check when making your booking. When budgeting, allow for an extra hour in case it’s needed and for any additional changes after the session.

If your mixes are on a number of CDs or mixed formats, make sure you have referenced them and can locate the right mixes on the day.