I had X3 - but I've upgraded.  I should be able to reinstall...  Thanks.

Sonivox Vocalizer pro is 90% off right now at Audio Deluxe for $19.99
https://www.audiodeluxe.com/products/audio-plug-ins/sonivox-vocalizer-pro
 
I picked it up recently and tested it with Platinum.  It runs as a MIDI keyboard controlled audio effect, for vocoding, re-synthesis and signal processing. 
 
Check out this demo session with the Sonivox lead sound designer, to see if it's something you could use.
https://www.youtube.com/watch?v=utI8d1eFgmc

I think that's what I'm looking for...  With the Holiday Discount it's only $16...  Worth a try - thanks for the head's up.  I'll give it a shot later.

mikebeam
I think that's what I'm looking for...  With the Holiday Discount it's only $16...  Worth a try - thanks for the head's up.  I'll give it a shot later.

Just fyi, the Vocalizer VST needs to be inserted as an audio FX.  But it also needs a MIDI track to play the Vocalizer from a MIDI keyboard.
 
Vocalizer Pro is a MIDI triggered audio effect, which is inserted as an effect on an audio track.  So don't forget to set up another MIDI track to send MIDI controller data to the Vocalizer plugin.  Then open the VST plugin window and enable MIDI input (via the dropdown arrow for the VST2 options) so you can play the effect from your MIDI keyboard (this enables you to select Output = VocalizerPro in the MIDI track).
 
This short video goes over the signal routing in Sonar X3 as an example:
Tutorial here: https://www.youtube.com/watch?v=I590YwC_bgA

Don't overlook the the Arturia MiniFilter V which is going free at the moment http://forum.cakewalk.com/FindPost/3534006
 
This looks a pretty decent effect with options to modulate both cut-off and resonance from a LFO, Step-Sequencer and an Envelope follower. Not a vocoder but a very useful free-bee none the less.

Glyn Barnes
Don't overlook the the Arturia MiniFilter V which is going free at the moment http://forum.cakewalk.com/FindPost/3534006
 
This looks a pretty decent effect with options to modulate both cut-off and resonance from a LFO, Step-Sequencer and an Envelope follower. Not a vocoder but a very useful free-bee none the less.

Downloading now.  Thanks for the tip!
 
Looks like this would be a great companion FX to have on board.  Especially when you just need a filter.  The modular approach 

Glyn Barnes
Don't overlook the the Arturia MiniFilter V which is going free at the moment http://forum.cakewalk.com/FindPost/3534006
 
This looks a pretty decent effect with options to modulate both cut-off and resonance from a LFO, Step-Sequencer and an Envelope follower. Not a vocoder but a very useful free-bee none the less.

Just a follow-up comment, but I'm really enjoying this!  Set the Low Pass Filter DRY/WET knob with a MIDI learn to your Mod Wheel.  So you can use it as an expressive effect. 
 
Besides the obvious approach of running a mono lead patch through this filter, a strings sample or a pad results in some interesting effects if you play with the wet/dry mix via mod wheel. The Pattern or Patternizer presets seem to work well with this method