Can anyone tell me the how to use the "ducking" process in Logic Pro 8?

You have to use the sidechain option that you can find on Logics' Compressor and on the Silver Compressor. You put the compressor on the track that has to duck, and the 'ducktrigger' signal you must select in the Sidechain dropdown menu that is on the top right of both those plugins GUI's.
In your example you put the Compressor on the Guitar track, and from the dropdown in Compressor you choose the vocal track as the sidechain.

Well, the theory is you run say, the mix , through the 'ducker' or as I like to call it, the 'motherducker', then you simply sidechain say, a kick drum. That is to say, you route your kick to a bus or aux channel, preferably routed to a different output, then assign that bus or aux as your sidechain input in the ducker. The theory is that the through signal will duck on receipt of the sidechained kick.

Frustratingly, this ducker is the buggiest thing since a bug landed on a buggy while loading it into the back of a VW bug. It just doesn't work. well it works for a bit and then stops working. Or the kick comes through the ducker as well. Or some other manifestation of complete crapness. Come on Apple, sort it out - it's the sound that everybody wants!

Sorry Mark L1

Well, as I see it, the ducker is one of those "easy Garageband plugins" to give people a one-click solution when they don't really understand the process.

Most of us will set up a sidechain compressor in the usual way, which gives much more control over the outcome, so that's the way I recommend going about it. It will give you an understanding of how and why it works, and the routing involved.

Sidechaining, for some reason, seems to be one of those things that really gets misunderstood by many people, but it's quite straightforward once you've got things clear in your head...

Message was edited by: Bee Jay

Well the most anlogue way of ducking things is to pull down 30+ channels whenever a kickdrum or any other sidechain signal plays - to make it more difficult route all the channels to an analogue Mixer without Automation and do it manually by inviting two friends (they should be musical hobbyists at least - ahh doesn't matter) of yours taking care of the other 20 faders. You probably won't get it in the first pass but it will sound completely ducked out of your mind.
I like the "Motherducker"..... 🙂

Quack!

You guys quack me up.