We spend an awful lot of time with a track when producing. We pour over each detail, honing every sound. But after hours of listening to a snare that is too loud, our ears simply become accustomed to that imbalance. When played back with other songs, the imbalance becomes painfully obvious. The irony is that our attention to detail can lead to a worse mix as we begin to lose an objective perspective the more we listen.
In psychology, this is known as the mere-exposure effect, the tendency to develop a preference for things simply because we are familiar with them. In music, we have to find ways to accommodate this psychological quirk. One common and convenient way to not lose an objective perspective is to compare your mix to a reference track - a professional song in the same genre with a similar sonic makeup. The goal here is not to copy the sound and balance of the reference track, rather, it’s to provides a benchmark so we can say "ah, my snare is louder than a normal track in the genre" and decide whether or not that's what we’re going for. In this way, comparing your work-in-progress to a finished song can take a lot of the guesswork out of mixing. Here, we'll go over how to set up your default template to incorporate reference tracks.
The Reference Track
First, you need to create a new audio track. This is where you'll drag a reference track onto, so label it "reference”. Change its output routing to ext. out 1/2 (or wherever you send your master output) to ensure the reference track doesn't run through the project's mastering chain. Then, mute the track - you don't want your reference to play with the rest of your song's tracks.
We'll be using a lot of key mappings for this technique. I've covered key mappings extensively before, but for this guide we'll be using some pretty simple ones - just key map the backslash key [\] to the reference track's solo button. Now you can switch between your song and the reference track with a simple press of the [\] key, since it's muted when unsolo'd.
This is pretty handy in itself, but we can take the concept a lot further by adding more techniques for comparing and analyzing your track and the reference.
As we all know, low frequencies are the most essential part of the mix to get right but also one of the hardest. A reference track can prove particularly useful for checking the balance in the low end, so we'll set up a filter that can be quickly engaged to isolate the bass in both tracks. I also like to check the high end between my track and the reference, so I have a high-pass filter built into my set also.
Let's start by adding two Auto Filters to the reference track. Make sure to switch these to clean circuit type if not already - we want as little added coloration as possible. Set the low-pass filter to 275Hz and high-pass filter to 2kHz. You can adjust these frequencies to taste, but those make pretty good starting points.
Next, you'll want to turn off the filters and key map the device activator buttons so they can be quickly turned on and off. I like to use the brackets [ and ] for low-pass and high-pass, respectively, as they seem the most intuitive.
Finally, copy both filters to the master track (make sure they go at the end of your chain, if you have one!) and map the same keys to their respective filters - [ for low-pass, ] for high-pass.
Now if you want to check the low end of your mix, you can just press [ and you'll hear the isolated bass. Of course, the reference track will also be filtered to the same frequency so you can use the [\] key to switch between low ends. This is useful to hear how your track's bottom end compares with the professional track, e.g. if there are unfiltered frequencies present from tracks that shouldn't be down there or excessive mud that should be balanced.
Another area you might find useful to check is mono compatibility - how your mix sounds when both of the stereo channels are summed to a single channel. This can be important for emulating how the song will appear on some club sound systems or small mobile devices. Setting this up is actually very similar to the filters - just add a Utility device to your reference track and key map the mono button to the [+] key. Repeat this process on the master, again remembering to put it at the end of any existing devices in the chain.
If your track is working as well in mono as the professional track, you're in good shape.
While we want to use our ears as much as possible, we can also view frequencies visually. Ableton’s Spectrum is great for analyzing a single track’s frequencies but for simultaneous comparison of two track’s spectra we’ll need an external VST - voxengo's SPAN - a free visualizer plugin.
Make two new audio tracks below the reference track and name them "a-master" and "a-reference". Then, create a return track [cmd + option + t] and put SPAN on it. Be sure to mute this return track as its purpose is purely visual and we don't want another copy of our audio feeding back. You'll probably want to collect all three tracks ("reference", "a-master", and "a-reference") into a group, as they should take up as little space as possible.
Set the "a-master" track's monitor to in and its output to sends only. Set the input to master and its input channel to post mixer, then pan the track hard left. Send the track to the SPAN return track.
Repeat the process with "a-reference", setting the monitor to in and its output to sends only. This time, set the input as "reference" (the original reference track) and its input channel to post fx. Finally, pan the track hard right and send it to the SPAN return track.
Now set up SPAN on your return track. Simply open up "routing" in SPAN and change the D group assignment to 2. Now go back to the analyzer and set underlay to 2. You'll now be able to see your track's frequency spectrum in green and the reference track's in orange.
You can compare frequencies at any time by opening up SPAN on the return track. Keep in mind that you don't want to over-rely on visual comparisons - the two tracks will probably use different instrumentation in different keys and so their frequencies will look a bit different. The whole concept of using a reference track is to establish a benchmark to see where you're at generally in your mix. If you can't quite achieve the sound of your inspiration, checking the spectrogram could call your attention to a major imbalance so you can fix it.
Saving To The Default Template
You'll want to make sure this system is saved to your default template (or a “reference” template) so you don't have to set it up for every new song. Make sure the reference track isn't solo'd, the group is collapsed, and the filters are both off. Then, open up preferences [cmd + ,] or [ctrl + ,] depending on OS and save to default template so that everything - the tracks, devices, and keyboard mappings - are all loaded every time you start a new project. All you have to do is put an appropriate reference track in the "reference" channel.