I'm embarrassed because I've done this before.  Took notes for future reference then misplaced them.
I want to route a lead vocal track out of DAW/Echo Layla/Sonar X1 into TC Helicon to get some harmonies.  What are the settings in Sonar and Voiceworks to do this. 
I have SPDIF and analog outputs and inputs from ECHO/Layla to Voiceworks. 
1. In Sonar vocal track out...SPDIF L or R? or Analog L or R?
2. In Sonar harmony track in....SPDIF L or R? or Analog L or R?
3. Within Voiceworks settings....Digital or Analog?....Sample rate?....Other settings to make this work?  For example even though a mic is not involved, I seem to recall that botton was on.
4.  After have the right settings, I'm assuming that I set the harmony to the recording mode as if I were recording from a mic but with the track "in" set as directed in number 2 above.
Once I've got the basic settings I'm sure I can set the harmony voices, and other features.
Thanks in advance for your help.

I would try digital first, since it is a digital effects.  No sense doing DA to AD to DA to AD, tho it probably won't harm anything going analog.  I don't have a voiceworks, so it is hard for me to know how it works.  But it should be a mono in and a stereo out if you are using stereo effects at all.
 
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Thanks AT for giving it a shot.  Will work on this in the afternoon.