by LMan

I made this quick crash course tutorial to share a basic impression of what's important for mixing and mastering on digital gear. There are some pointers, tips and hints to help you getting the most out of your freshly composed tune. I've got some info about compressors, mixing, and mastering.

Clipping

In a digital studio environment, clipping is to be avoided where possible. Clipping means, that your audio signal exceeds -0 dB, in the digital world that means any audio information beyond that point is irrecoverably lost. Almost every effects plugin, mixer, etc. has an indicator for clipping - and a knob/slider to reduce volume. Check at every possible station of your audio-route if there's clipping. The loss of volume you might notice doesn't really matter, you'll recover that during the mastering process. So make sure all your channels have enough headroom!

Compressors

Compressors are there to screen out loud peaks in audio. This usually helps to get a fuller, louder sound without reaching the clipping limits. Some claim that you can't employ enough compressors, but you must use them properly. It's not recommended to put the whole mixdown through a single band compressor, this usually results in pumping sound. Use compressors on single channels of your mix, especially on drums. Again I recommend to use at least 2 different compressors for your drum / percussion sections. I always route high frequency drums (Hihats, Cyms, Claps etc.) through one compressor, and the low frequency ones (Bassdrums, Toms etc.) through another one. You'll have to experiment a bit with the settings of the compressor to get your results, there's no basic rules for that.

The following settings should be basically found on every compressor device:

• Threshold
  The Threshold setting defines the volume level, from which above peaks will be affected by compression. That means: if you compress voice for example, and there's a loud sibilant exceeding the threshold level, it will be compressed. Special multiband compressors for exactly that task are called de-esser by the way.
  
  
• Ratio
  Means the relative amount of compression. A ratio of 2:1 for example would reduce the waves between threshold and peak to 50% (in graphical display: to half height). The higher the ratio, the more a compressor is becoming a limiter. A limiter is a compressor with a ratio set to a very high setting (like 1:16, or in some cases 1:infinite). This explains the term: the wave material is being limited to the peak volume defined by the threshold value.
  
  
• Attack/Release
  Here you can slow down the reaction times of the compressor. With drum sounds for example, it's often good to delay the attack of the compression. When the compressor detects a sharp attack, it will set in only after the attack time, and the first milliseconds of the drum won't be compressed. So the percussive drive of the sound is preserved. A suitable release setting helps with reducing unwanted pumping effects: the compression effect slowly fades away during the release time, after the audio signal is gone.
  
  
• Sidechaining
  If your compressor supports sidechaining, you can use one source audio signal to compress another. Know that pumping effect in house music (popular in "Call on me" by Eric Prydz)? That is usually achieved by sidechaining. Sidechain the bassdrum into a melody loop or a pad-like instrument's compressor, et voila. You may also use an otherwise inaudible signal for sidechaining, that way you can control the pumping effect independent of the bassdrum. You can do a lot of creative things with the sidechain, or pretty basic ones like getting a cleaner sound by ducking the bassline with the bassdrum.

You will improve your mixdown, if you keep every track in it's own frequency range. That means: Don't have too much bass in lead sounds, else you'll get your bass track all muddy. Don't have too much treble in lead sounds, or you'll drown your hihats. Don't have too much mid frequencies in your hihats, or you'll interfere with your lead sounds. You see where I'm getting at? It's just a pointer to keep your tracks acoustically separated - which results in a crystal clear sound. And don't be shy about it, this technique is the key.

Also avoid placing all the sounds at the stereo center. By moving accompanying elements left and right, you'll free up frequencies in the panorama and add depth to the mix.

Remove rumble from your channels by cutting away VERY low frequencies with a steep high pass filter set to about 20-30 Hz. That rumble might mud your mixdown without you realizing it. Those frequencies are rather felt than heard. It is also recommended to keep the very low bass sounds in the stereo center. Your ears cannot locate deep bass sounds anyway, that's why there is only one subwoofer in your 2.1 soundsystem.

Apparently it is useful to have good monitoring speakers when you are mixing/mastering. If you don't own one of these (like me), I recommend listening to the mix on various gear (headphones, big/small speakers, car) to detect flaws in your mixing. You should readjust mixing at least once after an appropriate break for your ears (preferably on the next day). You'll find it sounding very different from the day before… 😊 Walk through the room to get different impressions of your mix. There can be resonant spaces in your room, where i.e. bass frequencies sound very much louder than elsewhere. It also often helps to compare your mixing to a well-produced tune resembling the style you want to create.

Update 2020: I've now obtained a set of Yamaha HS-8 monitor speakers. It is indeed a whole different world, and making the mastering job so much easier. It also reveals all the flaws in my previous mixes that just were not perceivable on my old gear. So actually saving up on decent monitors is definitely worth it.

Still not getting a clear mix?

Start your mixing from scratch. Set all your faders to silence. Remove all the reverb and delay effects you thought you'd need during the creation of your track. Then, one by one, bring the channels back. Control their frequency ranges and panoramic positions. Leave the effects away for now. You'll see that your new mix will most likely have become crisper and cleaner.

Then consider bringing the reverb and delay effects back, but often less is more. I advise not to adjust those effects when wearing headphones, as you'll probably make your tracks too wet.

The following audio sample demonstrates a muddy mixing setup with all equalizers off. You can hardly make out some of the sounds, especially in the bass region.

The same audio clip, this time low and high shelf equalizers were used to put each channel into its own frequency range, and some sounds were moved away from the stereo center. The master levels and everything else is the same - see what difference mostly removing frequency ranges and subtle boosting can make?