- Try an exciter/ enhancer
If your top-end still isn't right despite your very best EQ efforts, you may want to try an exciter or enhancer. Whereas EQs can accentuate noise, and only amplify what's already there. Exciters improve the harmonics of the fundamental tones present in the recording, brightening dull mixes. Much like everything in mastering, though, don't overdo it!
- Narrow the mix
Adjusting the width of a stereo recording usually means rendering it wider, but an overly wide mix may be narrowed, too. You can find plug-ins that will do this, nevertheless they have to be handled carefully, as they could cause phasing issues and weaken a hardcore mix. Make sure you leave everything below 100Hz alone, as this area carries no directional information and has a much greater impact in mono than stereo.
- Noise reduction
You may want to apply noise reduction sometimes, especially during long fade-ins or -outs. This is often necessary because of bad recording or numerous other factors. Inevitably, though, if you don't have very high-end equipment, noise reduction will affect the harmonic content of the music to some extent, so there'll have to be some way of measuring compromise.
- Expand the dynamic range
Expansion may be useful for pulling some dynamics out of a squashed mix. Expanders work in almost the actual opposite way to compressors, increasing dynamic range as opposed to compressing it. They can't perform miracles, though, and can actually add distortion, so when you have to rely on a single, perhaps you need to consider having another go at the mix.
- Don't go through the ceiling
Keep your limiter's output (sometimes called the ‘ceiling') under 0dB. Although you may want your track to be as loud as possible, some CD players can glitch if way too many samples hit 0dB, and some disc duplication plants may reject the disc because their equipment determines the 0dB samples to be ‘errors '. Set your limiter to -0.5dB or thereabouts.
- Lookahead limiting
Some plugin limiters provide a lookahead function. This can cut the beginning of your track off completely if your left locator (export start point) is defined too near to a zero-crossing. So, if you use lookahead, leave an additional or two lead-in and -out for the bounce, then shrink the start and end of the last, mastered audio file.
- Put songs on separate tracks
When mastering an EP or album, import most of the songs onto separate audio tracks, so that all it's possible to have a unique EQ applied and the entire lot can be balanced accordingly. Route all of them to the exact same bus, then compress and limit them together for consistency.
- Try mastering reverb
Very rarely, you might want to use a mastering reverb to ‘glue'a mix together. Convolution is your absolute best option here, but avoid plate/spring emulations and be gentle with the wet signal - only 10-15% - and roll off most of the wet signal below 100Hz, too.
- Don't overdo it
Last however, not least - and at the necessary danger of repeating ourselves - don't overdo anything! Big EQ boosts, high compression ratios and/or super-low thresholds can ruin a track. You are able to still be creative while being subtle. Make sure to watch in your spectral analyser plug-in, ensure that the master channel never clips and learn to trust your ears. Here is the final process in the production of your tune, so it truly is now or never!