Synthshit

Add a glue compressor to a track- Click the arrow button shown below if you can't see the Side Chain option. Select the appropriate channel. Full Gain will get you ducking. Tweak the other bits to your liking! A "cleaner/better" way to do side chaining however, is to copy the piano roll from your ducking channel - eg. the kicks. onto a cleaner signal -eg. an Operator, set to a simple Triangle wave. The kicks will have all sorts of different attacks & decays, as well as noise in general, so using a seperate ducking channel, which you can just set to mute once it's all setup, is much cleaner.

To avoid latency, use the External Hardware Instrument device. Drag it onto a midi track. Generally, record the audio to a seperate audio-track, then disable the midi once you're done. Preferably record pre-fx, so you get a nice dry-signal. A loop note/trick -When the loop first starts, any reverb/echo will not be present. This can be weird, so it's worth recording an extra measure to use . Eg if your loop is 4 bars. Record 5 bars. Ableton can be configured to start at bar 1, but use bars 2-5 for looping. This way you get both a natural start and a natural loop.

Sometimes Ableton sets the bit depth of the PCM to values that aren't 16 bits... This will cause the software to crash on exporting video!