Sidechain Compression in Logic Pro: Complete Workflow

To sidechain in Logic Pro, put Compressor on the channel you want to turn down, then choose the trigger in the Side Chain menu at the top of the plug-in window. For kick-versus-bass ducking, Compressor goes on the bass and the kick is the external side-chain source. The kick drives the detector. It doesn’t pass through the bass Compressor.

This guide was verified against Apple’s current Logic Pro for Mac documentation on August 7, 2026. It covers direct track triggers, bus triggers, a silent ghost-trigger route, detector filtering, Max/Sum and Peak/RMS, musical timing, bounce/solo checks, and the failures that make sidechain compression appear broken.

Sidechain is an optional problem-solving stage in the complete Logic Pro mixing workflow, not a compulsory effect. Start with the hub when kick and bass might just need a different balance, arrangement, EQ or envelope before you build a trigger path.

Fast setup: insert Dynamics > Compressor on the destination, turn Auto Gain off, leave Mix at 100%, choose the trigger from the plug-in header’s Side Chain menu, open Compressor’s Side Chain panel, press play, lower Threshold until gain reduction follows the trigger, set Ratio for depth, then shape Attack and Release until the destination moves out of the way and returns naturally.

Sidechain compression has two signal paths

Ordinary compression listens to the same channel it processes. External sidechain compression splits those roles:

• Destination: the audible signal passing through Compressor and being reduced—bass, pad, music bed, reverb return, or another bus.
• Trigger: the separate signal feeding Compressor’s detector—kick, vocal, percussion, control click, hardware input, or bus.

Apple’s plug-in window guide confirms that a side-chain-capable plug-in can use an audio track, software-instrument track, hardware input, or bus as its source. The selected signal controls the plug-in, but it doesn’t get processed by it.

Set up kick and bass sidechain compression

1. Name the tracks clearly. Use names such as Kick and Bass so the source menu is unambiguous.
2. Insert Compressor on Bass. The destination—the sound that must duck—holds the processor.
3. Open the Side Chain menu in the plug-in header. This is Logic’s header above the Compressor interface, not the Side Chain button inside the interface.
4. Choose Kick. Search the menu if the project has many tracks and buses.
5. Open Compressor’s Side Chain panel. Start with its filter off so the full kick reaches the detector.
6. Turn Auto Gain off. Added gain can hide the amount of ducking and create an unfair comparison.
7. Play kick and bass together. Lower Threshold until gain reduction appears only when the kick triggers it.
8. Set Ratio for depth. Use enough reduction to create the intended separation without making the bass vanish.
9. Shape Attack and Release. Make the duck begin quickly enough, then let the bass return in time with the groove.
10. Bypass in the full mix. Match output and confirm that the low end is clearer or the movement is musically useful.

Apple’s Compressor side-chain workflow uses the same core sequence: insert Compressor, pick the source in the plug-in header, pick a detection method, and adjust the compressor. If gain reduction doesn’t move, diagnose the route before pushing the settings harder.

Set Threshold and Ratio from the amount of ducking

Threshold decides which trigger events produce reduction. That value belongs to the level arriving at the detector, so copying a threshold from another project won’t hold up. Lower it while the relevant section plays, and watch whether every intended kick, word, or control pulse crosses it.

Ratio controls how strongly the destination is reduced once the detector crosses Threshold. For transparent space, use a lower ratio and shallower threshold action. Go firmer when rhythmic pumping is the sound you’re after. Judge the destination, not the loudness of the trigger.

If only some trigger hits work, don’t drop Threshold straight to the floor. Check velocity variation, source processing, send level, and the detector filter. A dedicated control signal is often steadier than forcing a musical kick with shifting accents to perform two jobs.

Use Attack and Release to shape the space

Attack controls how quickly the destination is reduced after the trigger crosses Threshold. A faster attack separates the two sooner, but it can make the destination click, lose its front edge, or sound abruptly chopped. A slower attack keeps more of the onset, though the bass or pad can collide with the trigger before reduction develops.

Release controls how quickly the destination returns after the trigger falls back below Threshold. Too short can chatter or click. Too long can hold the bass, instrument, or reverb down into the next musical event. Watch the gain-reduction meter, then set the recovery by the groove and phrase.

There’s no universal “house sidechain” release time. Kick length, pattern, tempo, bass envelope, compressor model, Threshold, and Ratio all change the result. For a deliberate pumping effect, the audible swell may be the goal. For transparent ducking, the listener should notice the separation rather than the gain movement.

Use the detector filter without EQing the destination

Logic Compressor’s Side Chain panel gives you LP, BP, HP, parametric, and high-shelf filters plus Frequency, Q, and Gain. These controls shape the signal reaching the detector. They don’t filter the audible bass, pad, voice, or reverb return.

Apple’s side-chain parameter reference also provides Listen, which lets you hear the detector path while adjusting it. Use Listen briefly, then switch back before judging the mix.

• Direct kick track: start with the detector filter off. The source may already be clean enough.
• Full drum loop: use Listen and test a low-pass or band-pass shape if only the kick should trigger reduction.
• Vocal trigger: filter rumble or other energy only when it causes false triggering.
• Bass-heavy mix bus detector: a high-pass detector filter can reduce low-frequency overreaction, but that is internal compression—not external kick/bass routing unless a separate source is selected.

If the filter removes the very component meant to trigger Compressor, gain reduction stops. Turn the filter off as the first troubleshooting comparison.

Choose Max or Sum and Peak or RMS deliberately

For stereo side-chain sources, Max makes both destination channels compress when either side of the trigger meets the detector condition. Sum bases the decision on the combined trigger level. Compare them when a stereo trigger makes the image pull or the detector reacts inconsistently.

Peak detection follows short peaks. RMS follows an averaged level. Peak is a practical starting point for a short kick or click trigger. RMS can better follow sustained vocal or music-bed energy. Apple notes that these choices interact with Max/Sum and can help avoid artifacts depending on the material and Attack setting.

Use a bus when several signals must trigger one compressor

A direct track source is simplest for one kick and one bass. Use a dedicated trigger bus when several kicks, percussion layers, or vocal channels must control the same Compressor, or when the detector needs its own stable level. If bus and aux roles aren’t clear, map the route first with the Logic Pro buses, sends and aux guide.

1. Choose an unused bus and name its aux channel Sidechain Trigger.
2. Create sends from each trigger source to that bus.
3. Choose Pre Fader when trigger strength must remain independent of source fader and pan moves.
4. Balance the send levels so the combined trigger represents the control you want.
5. Select that bus—not every source individually—in Compressor’s Side Chain menu.
6. Press play and verify that the gain-reduction meter follows all intended events.

Apple’s send-routing documentation confirms that Pre Fader is unaffected by the source fader and pan. Post Fader follows volume. Post Pan follows both volume and pan. Pick the tap point by whether mix moves should also change the detector.

Build a silent ghost trigger you can verify

A ghost trigger is a dedicated control pattern that isn’t meant to be heard. It keeps ducking independent of the audible kick’s sample length, fill pattern, or mute automation.

1. Create an audio or software-instrument track containing the control pulses.
2. Send it Pre Fader to a dedicated bus named Ghost Trigger.
3. Set the receiving aux channel’s output to No Output so the control bus does not feed Stereo Out.
4. Keep the trigger track and aux active; do not use Track On/Off to silence them.
5. Select the Ghost Trigger bus in each destination Compressor’s Side Chain menu.
6. Verify the gain-reduction meters during normal playback.
7. Bounce a short test and confirm the ducking survives the exact offline/solo workflow you will use.

This route separates detector level from audible level without depending on whether a particular mute or solo state keeps feeding a direct side chain. No Output is for the audible destination of the aux. The bus itself remains the selected detector source. Keep the route simple and avoid sending the destination back into its own trigger bus.

Ducking a vocal, music bed, or reverb return

Make instruments yield to a vocal

Place Compressor on the instrument bus and choose the lead vocal or a clean vocal bus as the trigger. Use modest gain reduction and a release that restores the music between phrases without an obvious inhale. This can improve intelligibility, but arrangement, automation, and tonal masking still matter.

Duck a reverb behind the dry vocal

Send the vocal to a reverb aux, then place Compressor after the reverb on that aux. Choose the dry vocal as the side-chain source. While the singer performs, the return moves down. After the phrase, Release lets the tail rise. The dry vocal stays outside that Compressor.

The Logic Pro vocal-mixing workflow explains how editing, EQ, compression, de-essing, shared effects, and automation work around this route. If every syllable should move the reverb by a different amount, automate the send or return instead of forcing one detector setting to solve the whole performance.

Sidechain compression does not automatically fix masking

Kick-to-bass ducking turns down the entire bass signal for a moment. That creates time-domain space, but it doesn’t selectively remove only the overlapping frequencies. If the kick and bass still sound muddy between hits, inspect arrangement, octave, envelope, phase relationship, and EQ rather than pushing ducking until the bass disappears.

Not every clean low end needs sidechain compression, either. A short kick and well-shaped bass may already coexist. Bypass at matched output and keep the route only when it improves clarity, headroom, groove, or an intentional pumping effect.

Troubleshoot sidechain compression in Logic Pro

Final sidechain checklist

• Compressor is inserted on the destination that should duck.
• The trigger is selected in Logic’s plug-in header Side Chain menu.
• The detector—not the destination audio path—receives the trigger.
• Auto Gain is off while depth and timing are set.
• Threshold catches the intended trigger events.
• Ratio creates only the required amount of separation.
• Attack clears the collision without clicking or chopping the destination.
• Release returns before the next important destination event.
• The detector filter is off unless it solves a defined false-trigger problem.
• Bus send position matches whether fader and pan should affect detection.
• Playback, solo, and bounce all preserve the trigger route.
• The full mix improves after a level-matched bypass.

Use the Logic Pro tutorials hub for the surrounding recording, routing, automation, and mix workflows. For level changes that must follow musical sections rather than another signal, the Logic Pro automation guide is the more direct tool.

Frequently asked questions

Where does Compressor go for kick and bass sidechaining?

Put Compressor on the bass, because bass is the destination being reduced. Choose the kick as the source in the Side Chain menu at the top of the plug-in window.

Why is sidechain compression not working in Logic Pro?

Check the insert location, selected source, active trigger signal, Threshold, Ratio, Mix, Auto Gain, and detector filter. The gain-reduction meter should move when the trigger plays.

Does the sidechain signal pass through Compressor?

No. The external source controls Compressor’s detector; it is not routed through the destination’s audio-processing path.

Should a sidechain bus be pre-fader or post-fader?

Use Pre Fader when detector level must ignore source volume and pan changes. Use Post Fader or Post Pan when those mix moves should also change the trigger.

How do I make a ghost trigger silent in Logic Pro?

Send the control track Pre Fader to a dedicated bus, set the receiving aux output to No Output, and select that bus as Compressor’s side-chain source. Verify playback and a short bounce.

What do Attack and Release do in sidechain compression?

Attack sets how quickly the destination turns down after the trigger crosses Threshold. Release sets how quickly it returns after the trigger falls below Threshold.

Does sidechain compression fix kick and bass frequency masking?

It can create time separation by lowering the whole bass signal around each kick. It does not selectively repair every overlapping frequency, so arrangement, envelope, phase, and EQ may still need work.