Another option that I usually prefer when the sidechain source is more complex is to convert it to MIDI. It may be a very simple underlying rhythm that you want to sidechain so you could even just write out the MIDI and repeat it.
But there are tools available to speed this up.
JS AudioToMIDI effect is very effective. Route audio from your kick track to a new track with this effect on it and dial it in. Test it by putting a sample trigger on it of any sort.
Then render the track to MIDI to gain fine control. Stretch all the notes out to a larger size, even overlapping each other. Then run the action 'Correct overlapping notes'. Now you should have large notes and short notes. Use MIDI editor note filter to select notes that are shorter than your quarter notes and remove them or move them to a separate track if you would like to for example still use them for sidechain but just not as much.
Optional step: fix up the velocity of the notes or even just set them all the same. An easy way to range limit velocity without adding a plugin is to simply select all the notes, drag their velocity up or down until the lower/upper limit starts moving the velocities into a straight line of 0 or 127. Let go, then drag back up/down.
But I find for the purpose of sidechaining on most kick drum tracks that actually a steady consistent velocity of the MIDI notes makes for a more consistent dip in volume on the bass and you can afford to be more subtle with it.
Lastly, send this MIDI to an envelope filter like DADSR like Zenvelope (
https://forum.cockos.com/showthread.php?t=152382 ) on the track to be sidechained. Total control over the sound.
Other perks of using MIDI: you can easily adjust the timing of the sidechain by simply moving the notes forward or back. Back is great for kick and bass sidechain because you can use a generous attack setting on the envelope filter so you don't mess with bass transients as much. Quite transparent.
Sidechain: duck only on full 1/4 notes
Linear Mode
