OCTOBER 22, 2021

Mid-Side Processing Made Easy


Pro Tools' multi-mono mode is great because you can process the right and left channels independently—you're not forced to apply the same processing to both channels.

However, mid-side processing is more difficult. Fortunately, the T-RackS SE suite of plugins from IK Multimedia is available for a limited time as a free, non-expiring download for Pro Tools subscribers. Two of the plugins do native mid-side processing within Pro Tools, which is useful for many applications.

Mid-side processing encodes the traditional left and right stereo channels into two different channels:

  • The mid channel sums the left and right channels, as if you had panned both to center (which gives a slight center boost due to mono build-up).
  • The sides channel is what the left and right channels don't have in common. The more the audio is panned left or right, the more it's part of the sides.

The T-RackS processors decode the mid and side audio back into stereo. So, even while processing the mid or sides, the output (i.e. what you hear) is conventional stereo. Insert these as multichannel plugins.

The following video shows how to do mid-side processing instead of the default left/right processing.

0_1200x600_Intro Choose Mid or Side

Application #1: Get a More Prominent Stereo Image, with No Phase/Summing Issues

1_1200x600_Raise Sides

Increase the sides level (or lower the mid level) to emphasize the stereo image's side.

  1. Insert the T-RackS Classic Equalizer (but we're not going to use it as an equalizer).
  2. Choose M/S mode, and select S.
  3. Raise the equalizer's output level. This boosts only the sides, not the center, so the sides become more prominent.

Application #2: Widen the Stereo Image

2_1200x600_Widen Image

High frequencies are more directional than low frequencies. Increasing the highs for only the sides widens the stereo image by making the difference between the right and left channels more distinct.

  1. Insert the T-RackS Classic Equalizer.
  2. Choose M/S mode, and select S.
  3. Enable the Hi shelf. Increase the highs slightly to emphasize the separation between the right and left channels and widen the stereo image.

Application #3: Prep for Vinyl Release

3_1200x600_Prep for Vinyl

A stylus has a hard time tracking low-frequency grooves if the bass isn't centered. The old-school fix was just cutting the bass somewhat, but we can do better with mid-side processing.

  1. Insert the T-RackS Classic Equalizer in a track that has a significant amount of non-centered bass.
  2. Choose M/S mode. Select S.
  3. Enable the Low Cut filter. Raise its frequency to find the sweet spot of good sound with less bass.

Remember that the mid is the sum of left and right channels. If there was a significant amount of bass in the sides, increase bass in the mid to compensate.

Application #4: Drum Room Mic Compression for LCR Mixing

4_1200x600_Compress Room Mics

Fans of LCR mixing—where tracks are panned either hard left, hard right, or center—often use left and right channel room mics on the drums to fill-out the stereo field. Compressing the sides can bring up the room mics more, without affecting the kick, snare, and other centered drum kit elements.

  1. Insert the T-RackS Black 76 Limiting Amplifier.
  2. Choose M/S mode. Select S.
  3. Adjust the controls for the desired amount of compression for the sides.

Application #5: Separate Mid and Side Processing

5_Separate M-S Processing

You can use any effect to process a track's mid and sides. Please refer to the image above.

  1. Create a bus for the track to be processed (e.g., Drums), and route it to two Aux Inputs.
  2. Insert a T-RackS Classic Equalizer in each Aux Input.
  3. Choose M/S mode for one. Select M.
  4. Turn the Output control down all the way. Now this track passes mostly the sides.
  5. Choose M/S mode for the other. Select S.
  6. Turn the Output control down all the way. Now this track passes mostly the mid.

For example, you can process only the sides with reverb (like IK's CSR Room, also included in T-RackS SE), and the mid with a compressor, like the Black 76.

Of course, this is just a taste of what mid-side processing can do! Download the free T-RackS SE plugin suite to explore the possibilities further.

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