By "mastering" them - meaning, by balancing each individual song against the others in level and sound to create a coherent, satisfying whole.
Many of my posts are squarely aimed at people who want to get as close as they can to having their CD mastered by a professional. However these tips and suggestions are more general and will benefit anyone who wants their CD to sound good - they apply equally, regardless of the level or standard of your mastering skills.
- Think big - Mastering is about making an album from a collection of songs. Now isn't the time to agonise about the details - whether the vocal is too high in one song, or whether you should add another guitar part to another. Mixing is over - move on ! Think about how songs relate to each other, look for a "line" through them, so they flow convincingly. I often describe mastering as finding the "centre of gravity" of a collection of tracks, and helping them all sit right next to each other. Listen to the overall sound of each song, and work on that.
- EQ and volume are everything - The equalisation (broadly speaking the bass, middle and treble balance) of each track needs to be right before anything else will work. To choose the right EQ, the level needs to be right, but the EQ influences what level you choose. Sounds like a Catch-22 ? It is. So, set the level, adjust the EQ - repeat until happy. Of course dynamic compression is a crucial part of this process - see below.
- Have an open mind - Normally my advice to people is "don't try to master your own stuff". If you are trying to do it yourself though, throw away all the pre-conceptions and ideas you have inherited from the recording and mixing process, and start afresh. Be prepared to cut swathes through all the detailed decisions and reasoning you've put into the project so far - a mastering engineer gives an impartial, third-party opinion about what's best for your material - you need to try and do the same. Listen to the Big Picture.
- Match vocal levels - When choosing how loud each song should be compared to the others, it's easy to get confused. A great rule of thumb is to balance the vocals. If you can get the vocals for each tune to sound as if they're in the same ballpark, almost anything else will work around them. Where you don't have a vocal to listen to, pick the main melodic element instead.
- Work fast, be bold - Use broad brush-strokes; listen to each song and make big, instinctive changes. Set the level, choose an EQ and go for it. Instinct is important in mastering, and often your first thought is the right one. If you find yourself going around in circles worrying about the details, it may be best to move on to a different song and come back later.
- Keep it Dynamic - You can master a CD without boosting the overall level at all, and all the EQ and level adjustments will still be invaluable. However most people also want to lift the overall level to be closer to commercial releases as well, and so compression and limiting become important parts of the process. I'm writing a whole series of posts about this, but the main point to make here is - don't be tempted to over-cook it. Music needs light and shade - without Quiet, there can be no Loud. So strive to find the "sweet spot" for your album, where the benefits outweigh the problems compression and limiting can cause. If in doubt, check out my post How Loud Is Too Loud ? Don't let your CD be a victim in the Loudness Wars - no-one wants to be the next "Death Magnetic"...
- Good gaps - mix it up - The silence between tracks on your CD can sometimes be as important as the tracks themselves. If a gaps are too short, the album can feel rushed and exhausting - too long and the listener is distracted form the flow of songs wondering where the next tune is. Some people swear by two-second gaps, but my favourite rule of thumb is - make the gap equal to two bars of the out-going song. Times to consider breaking this rule are early on on the album, where you might want to build momentum, or after a song with a slow fade. Occasional longer gaps can give the listener time to catch their breath, or frame a change of mood or style, for example. Variety is the key here.
- Burn Slow, Burn Steady - So your songs are sequenced, balanced, boosted and spaced - all you need to do is burn a quick copy at 52x and listen, right ? Wrong. Different brands of CDRs work better in certain burners than others, and error rates vary widely depending on the write speed. Yet again this is a complicated topic, but on the whole we see the best results burning at slower speeds like 16x, 8x or even 4x. This isn't such a big issue unless you want to use your CD for replication, but avoid the very high speeds, and spend a little more on "name" brands like EMTEC, TDK or Verbatim. If you want to use what we use, these brand-names are no use, though - the company widely-regarded as producing the most reliable CDs of all is called Taiyo Yuden - but not all suppliers can offer them.
If your goal is to try and get a professional result for a CD release, all the above techniques will help you. You'll also need decent monitoring in a reasonable room, and probably to read all my other DIY mastering posts - but you'll find the ideas here equally valuable, even if your goal is only to make your band's demo sound as good as possible, or you just want to make a better-sounding mix tape.
I hope you find them useful, let me know how you get on trying to put them into practise.