Ducking will ‘duck’ or downward compress the wet signal to the dry signal. This is useful to ensure the wet signal doesn’t drown out the dry signal, and to clear room in the mix. Everytime dry signal is detected, the wet signal is compressed downward to clear room, and returns to full level depending on the Release settings. Sidechain will ‘duck’ or downward compress the wet signal to the signal from another track. For example you could pump a Butterfly Effect’s wet signal from the rhythm of a kick drum. You will need to set the external signal (ex. the kick drum in this case) as the ‘key input’ on the plugin or track in your DAW. The Frequency knob controls which frequencies are downward compressed in Ducking and Sidechain mode. For example you can duck mid/low frequencies to clear room in the mix, while not touching the high frequencies which are more easily audible when ducked. So room is created in the mix and felt, but the ducking isn’t heard as easily. Moving the Frequency knob engages ‘listen’ mode, which isolates which frequencies are being compressed. Release time determines the release time of the compressor in the ducking and sidechain modes. Sync will synchronize the release time to note values based on the session’s BPM.