Compression question
Hi all,
I've been experimenting and learning while doing, with compression on my tracks, in particular this side-chain business for kick and bass, which is a great trick which has opened my eyes and ears to all the professional music around me. Many thanks to all for your wonderful forum-advice so far 
While experimenting, I noticed a dial on NS2 Compressor called HOLD, which I didn't see on other compressors. Now if my instinct serves me, this would be like the D or the S in ADSR waveforms, so the compressor has Attack time, Hold time and then Release time. A quick google seems to confirm this idea.
What I would like to know is - how do people use this in their projects? Do they use it? How do you all decide what time settings to use for the attack, hold and release dials, without knowing the number of milliseconds that the kick lasts, for example?
At the moment I'm sort of winging it by ear, for my sidechain compression settings; a pretty fast attack to duck the synths&bass at the very start of the kick, and then a little bit of hold to allow the kick sound through, then a fairly quick release to bring the synths back in. If I get lucky I can time the synths to come back on a 1/4 or 1/8 beat which seems to sound pretty nice. But my sense is that there could be a more scientific / mathematical /professional route for these millisecond choices. 
I realise it's a BIG topic, so am just interested for any obvious pointers and tips, or 'usual practice' ideas, to get me pointing in the right direction - thank you!
Comments
I’ll be honest and say that I’ve never used the ‘Hold’ function. I would also be interested in others replies.
As for compressor timings, I’m not sure if there’s any equations, but I do it solely by ear. Fast attack and set the release to suit the rhythm of the track. Extreme settings help you to get it right, then you can back it off.
Some use a short click or percussive sound instead of a kick for triggering the sidechain.
Depending on the frequency of the trigger , you can adjust that on the compressor too to match the input signal.
one tip - filter on compressor is handy not just for filtering sidechain input in case it is connected to compressor - it is useable also in case of not connected external sidechain input, compressor uses it's own audio input (audio which is compressor actually compressing) asown internal sidechain source automatically - using filter you can filter this signal to get different response of compressor
example
you drumloop is now sidechained by just kick from that drumloop, because filter effectively filtered out everything else :-)
same way if you turn filter to the left, now your loop is sidechained by just hinats :-)
you can get pretty interesting effects..
Interesting. Didn’t know that 😉
Thanks all, for your comments. Inspiring stuff as always
Hold is good for creating a space after a hit, if you want to either emphasize the hit or create a space for something else to fill in, basically just a delay before returning to the full volume of the track. You can do that with decay but you can really sculpt the shape of that space by combining the two.
I use a silent 909 kick for triggering the SC regardless of the actual kick used in the track but I also sidechain melodic elements that clash and frequently I duck pads when vocals hit.