Did a quick search for this, was sure someone would have done it, but didn't find anything.  What I want is echo that comes in after the singing phrase ends.  So the singing stays clear but then discrete echos (not reverb) happen afterwards.  A la Pink Floyd.  Surely someone has patched up an effect to do this.
 
CAF

It's a fairly easy set up using a compressor and sidechaining. You use the vocal signal as the sidechain so when there is sound the echo is ducked. When the vocal is quiet the compressor opens up and lets the echo "breathe".
Hopefully you know how to set up a bus (for the echo and compressor) and sidechaining.

Grum.

I did with piano track on one my songs. What I did was 1. Add the Sonitus:fx Delay plugin onto a new buss track. 2. On the piano track I created a send to the delay buss track. I then used automation on the piano track control to control the delay send to only send to the delay buss when I wanted the echo effect.

OK, I think I see how to do it.  I see the Sonitus compressor exposes a side chain input that I can route to from any track.  That makes it pretty straight ahead.  Thanks.

CAF

The Sonitus gate can sidechain too

grumbleweed4162

It's a fairly easy set up using a compressor and sidechaining.

I'm struggling with the easy stuff.  I think I understand the principles of sidechaining, but in practice I have only had limited success with it.  Looking at the Sonitus Gate or Compressor, it is not obvious to me what to adjust to achieve an effect involving sidechaining.

I have been trying to do something similar to what the OP is asking, except using reverb rather than delay.  I want the reverb to be activated at the end of every vocal phrase, but not audible at other times.

You can use side chain. If I were to do it I think I would route a send to the echo buss and automate the send enable/disable.

Tom Riggs

If I were to do it I think I would route a send to the echo buss and automate the send enable/disable.

I've been using envelopes to automate send, but with dozens of short phrases it's very fiddly and taking forever.  I am seeking an alternative using ducking or something.

  If I understand what you are trying to do, I would cut the words that you want echo on into separate clips and then apply echo directly to the clips effect bin or drag those clips to there own track and add delay to that track

At first I thought you folks were crazy who wanted to manually manipulate, but after setting up the sidechain, I couldn't find any automatic settings that seemed to give me the musical effect I was imagining.

I can turn the ratio way up on the compressor and set the threshhold low so that it effectively turns off the delay during the main vocal, but then when it comes up, it comes up a little too often and pokes thru even breaks in the middle of a phrase (of course).

I don't think I'll spend the time to cut into clips or fiddle with automation.  I mean, maybe if I thought I was working on Dark Side of the Moon...

Thanks.

CAF