A previous Friday tip, Mid-Side Processing with Artist, was published in June 2021. Since then, I’ve found a less obvious, but simpler away to accomplish virtually identical results.
To simplify, mid audio is what’s centered in a stereo track. Sides audio is what’s panned off to the sides. This tip extracts a stereo audio track’s mid audio to one console channel, and the sides audio to a second console channel.
Once extracted, you can process each element separately. This can be as simple as changing the balance between the mid and sides, or as complex as adding signal processors (like reverb to the sides, and equalization or delay to the mid). A common technique is increasing the sides level to widen the stereo image.
Obtaining the Mid and Sides
The mid is simply both channels of a stereo track panned to center. So, the mid also includes what’s in the right and left sides, but the sides are at a lower level. This is because anything the left and right channels have in common will be a few dB louder when panned to center.
The sides first reverses one of the stereo channels before mixing them into dual mono. So, whatever the two channels have in common—namely, the mid audio—cancels out. Following the dual mono signal with a second phase reversal restores the signal to stereo, and corrects for the original phase change.
Fig. 1 shows the setup for how to extract the mid and sides audio from a stereo console channel.
How to Extract the Mid Audio
The Mid pre-fader send from the Stereo Audio track feeds the Mid console channel. Set the send level to 0.0. The Mid console channel includes a Dual Pan. Select the Dual Pan’s Mono preset. This is all that’s needed to extract the Mid audio in the Mid console channel.
How to Extract the Sides Audio
This extraction process is a little more complex. The Sides pre-fader send from the Stereo Audio track (also set to 0.0) feeds the Sides console channel. The first Mixtool inverts the right channel. For the Dual Pan plug-in that follows the Mixtool, again choose the Mono preset. (You want both Dual Pans to use the same pan law.) Because the right channel is out of phase, the Dual Pan’s mono output cancels any audio the left and right channels have in common. This produces the sides audio.
To convert the sides audio back to conventional stereo, the second Mixtool inverts the right channel’s phase. Now, the sides are extracted, in stereo, and in phase with each other.
Mixing with Mid and Sides
With this method, you’ll need to mix the mid and sides level individually:
When the Mid and Sides balance is correct, group the two console channels. To do this, select the two tracks and type Ctrl+G. This also gives you the option to name them. Now you can set both levels by moving either fader.