When mixing or mastering it's a great idea to have a few commercial tracks lined up so they can be heard at the touch of a button. If you're getting lost or sucked into the track you're working on, it's a great refresher to hear other music; to "clean the ears" sonically. Referencing is a valuable production aid but also one that is often overlooked, or implemented wrong. If you use reference tracks in your workflow already there might be one or two things here that will help you get the best from them.
This is a very easy mistake to make and a hard one to catch once it's happening. So here's an explanation. When using references during mixing, if you set up the reference track in your software it will probably be going through the master channel directly like every other instrument. Which is fine if there are no effects on the master channel, but if there are then the reference track will be receiving this processing too.
Imagine you're trying to do a simple mid-frequency boost on your own mix before sending it to your mastering engineer. Maybe so you can give the whole track a bit more middle, so it matches the references more closely. So to do this you:
Now as you perform this mid frequency boost, aiming to boost only your own track, you're actually boosting the mids of the reference track too. Because both tracks are going through the master channel, when you switch over to hear the reference track it will have even more mids than before. This way you'll never get them to match in the way you want and both your track and the reference will start to sound very strange, very quickly as you boost and keep boosting!
The solution to this is if you need to perform any master channel work for your own song, you should route all your instrument tracks through a stereo mix buss in your DAW (or hardware mixer) and apply any "master channel" style work here, instead of on the actual master channel. This will leave the real master channel clean and the reference can now play through unhindered, leaving your own track to play through the mix buss with the desired mastering effects.
This should probably be number one, but if you're not routing the reference probably as we've just described, then everything else won't really matter!
So, when a lot of people think about using reference tracks, they think about using spectrum analysers, EQ curve matching tools, analogue-looking VU meters etc. to compare the references with their own songs.
Please don't use them.
Just use your ears to compare.
To speak about it technically, spectrum analysers only approximate how our ears work. RMS and peak meters only approximate slow and fast changes in the music. It can be demonstrated that two entirely different sounds can be made to look the exact same on a spectrum graph or EQ curve matching tool. I could go on about the technicalities and the complexities of how the human ear hears things psychoacoustically, but I want to focus on ear training. That's what we mean when we say "use your ears, not your eyes".
I believe the true way of improving your production skills is by training your ear to hear better. This isn't something that comes overnight but if you can make a small advance in improving your listening skills by practising a bit, then this is worth much more than what any visual device can tell you.
So ignore all metering (if there's unwanted clipping or distorting you should be able to hear it, right?), ignore all spectrum analysers and ignore any unnecessary visual aids.
Make changes because your ears told you so.
Even better. Close your eyes!
Okay you can open them now.
As you get into making more subtle tweaks, you want to make sure that changing between hearing your track and hearing any reference track is instantaneous. If there is any gap the brain has some time to adjust and your ability to compare the two will be greatly reduced.
Probably the easiest way to set up your reference tracks is to place them on new stereo tracks and then mute those tracks. Now whenever you want to hear the reference all you need to do is press the solo button. Your track will cut out. The reference track will sing through.
Again, this is connected with the idea of avoiding all visual metering and aids. Make sure you match the volume of all the reference tracks to the track you're working on...
Remember two things can look the exact same on the meters but sound totally different in terms of how loud they sound. Use your ears to match the the levels by perceived loudness, by how loud it sounds to you.
In making them sound the same perceived volume you'll be able to properly compare their differences and won't be fooled by the cardinal rule of loudness which is, "louder sounds better to ear". The psychoacoustics of loudness is a complicated thing but by matching the loudnesses by ear, your brain won't be tricked into thinking something sounds better.
When all along, it was just a little louder.
Mastered tracks will mostly be louder than the track you're mixing. Instead of boosting your own track (and risk running out of headroom and distorting or clipping the mix) pull the level of the reference tracks down and match them by ear to yours. This way you get a sensible amount of headroom to work with and again you won't be fooled by the louder=better phenomenon.
I feel this is quite an important one.
Use multiple reference tracks, maybe three or four or even more.
The problem with using just one reference track is it's very easy to fall into the trap of trying to match your track exactly to it. What you end up doing is mixing up these two similar but conceptually different notions:
It's easy to think that your track isn't yet up to the quality standard of the reference, when in fact your brain is actually asking the question, whether or not the track sounds like the reference.
This is substitution bias in action (see Kahneman et al), and quite a big concept so pause to think about it for a moment.
Don't be trying to make your tracks sound like the references, try to make them sound as good as the references.
Line up a few commercial tracks from artists that you like, match them for volume by ear and then switch between them.
What do you hear?
They all sound good right? (You did pick ones you like?!)
They sound good, but different.
They'll probably all have roughly the same amount of bass and treble (although even this will vary depending on the song) but not exactly the same amount. They'll actually vary quite a lot if you listen closely (or even not so closely!).
The fact is, commercial tracks, ones you like, have different tonal balances. They sound different. Difference, like in real life, in my opinion should be celebrated.
So if tracks sounding different is okay then why are we using references to compare for similarities at all?!
Well, this brings us to...
When you're using references, you're using tracks you know well to refresh your ear and remind you of the sonic space you're working in. Have a few lined up that have different sounding frequency balances, so you can use a reference that's very bass heavy and remember as you listen, "Okay that's roughly the maximum bass level I'd like in my track". Use a track that has good sounding but sharp and prominent cymbals, and think "If my cymbals are sounding harsher than this track then I may be pushing the treble area too hard". Use a track with good vocals, even if you're making instrumental music just so you can remind yourself what sounds natural.
Think ballpark. Think approximate. The aim here isn't to try and exactly spectrum match your track to another track, the references are there as an aid for general bass and treble levels, and to remind your ear of the sonic space you're working in. Think left-to-right for stereo width, think top-to-bottom for treble to bass and think near-to-far for dry, up front sounds to reverb-drenched, distant sounds.
When you find yourself using references in this way, to earmark a three-dimensional sonic space in which to work, you'll find that you're starting to use references correctly. You'll know by comparison when you've pushed something outside of that desired space and it'll begin to become instinctive as you get to know your references more intimately.