I am recording an a capella piece with several voices; I've used Melodyne fairly extensively to tighten timing and to some degree pitch.  When I'm tracking additional singers, I get frequent cracking and popping - pretty sure it's at each clip juncture, and I assumed due to the processing of the Melodyne-altered clip.  (If I Mute all edited clips, the cracking stops.)  For tracking, I have my ASIO audio buffer set to Minimum to minimize real-time latency.  (If I set it to maximum for stability, all the cracking disappears, but there is too much latency for tracking.)
 
Here's where my problem comes in.  The cracking is too distracting for the vocalist - plus there is cracking being recorded in the new track.  So I tried Flattening the Comp, assuming that would remove the processing and get rid of the cracking - no go.  So I went through one of the edited tracks and bounced each edited clip to removed the Melodyne processing.  I am STILL getting the cracking and popping unless I set the buffer to Maximum.  So I edited by Read Caching and Write Caching (more than doubled Read caching and doubled Write caching) under Synching and Caching.  I think it improved the amount of cracking, but it's still very much present.
 
(1) How do I get rid of the added noise for tracking additional vocalists?
(2) Why is the noise still there even though I've bounced to clips - shouldn't I be back to a simple audio clip at that point that is using minimal resources?  Or am I barking up the wrong tree?

Instead of bouncing each clip, freeze each track that has Melodyne on it to release the cpu cycles that Melodyne is using and you can always unfreeze to continue editing.

That works, thanks!
 
But why am I getting the added noise even after bouncing to clips?  Shouldn't Melodyne NOT be processing anything at that point as well?  (Or perhaps it's not Melodyne - but I don't have this problem in a similar project with the same vocalists where I have NOT used any Melodyne editing yet.)

Turn off fast bounce.

if you bounce, did you suspend the Melodyne plug in the original track? If not, it's still running.
 
Try this.... first save the project with a new name. This ensures that you are NOT working on the original and only copy of the song. Now insert melodyne and do the processing. Now, select the entire track where melodyne is located and use PROCESS AUDIO  to let Melodyne print it's output to that track. It also removes the melodyne plug in and leave behind a wave track....very little processing required by the DAW to run a wave track.
 
See if that solves the problem.
 
I use the Process Audio function all the time with melodyne. It's destructive but hey, I don't want or need the original out of tune track. If you missed something, you can always reinsert MEL and have another go at it.
 
Work with it in the MANUAL mode and not in the automatic mode. That way, nothing gets messed up that can't be undone with a few mouse clicks. All changes are deliberate and you can check them before moving on.

I follow what you're saying, Guitarhacker - but I'm not finding a way to PROCESS AUDIO for the entire track.  I split the vocal track(s) into phrases, and only edited phrases that needed time adjustment to be tight.  I suspect I need to process audio for each of these clips independently to accomplish what you're recommending, correct?
 
I assumed bouncing to a clip translated the MEL-edited clip into a WAVE clip and closed the editor.  It sounds like the MEL-clip is still present and being processed even though I'm not hearing it?  (When I bounced each clip, it visually appeared in another take-lane, and the original take-lane visually is blank.  But it sounds like the previous clips may be hidden behind the new clip?)

Perhaps I am not processing the audio effect properly; but I just realized in attempting to follow the recommendations I ended up with all unused (muted, and non-MEL-edited) clips in the entire track converted to stereo clips; and the Melodyne-edited clips still appear as Melodyne-edited clips with no processing having occurred.  I right-clicked in the track composite waveform, selected Process Effect -> Audio Effects -> VST3 -> Celomony -> Melodyne.  The Melodyne editor appears but with no waveforms showing.  After selecting OK the above occurred.
 
(With the desired track selected, Process -> Apply Effects -> Audio Effects is grayed out.)

Make sure your ASIO buffer is high enough (like 1024 samples).
 
Go to Preferences | Drivers | ASIO panel.
 
If you're not using ASIO, then never mind. 
 
 

If I set the buffer high there is no issue.  (Although when I slide mine all the way toward Maximum I only get 960 samples; Melodyne user manual suggests 1024 as you note.)  But when tracking other vocalists I need a lower setting due to latency.  I've realized Melodyne is too CPU-intensive to have it on with other tracks while tracking. 
 
I'm still confused by why I get identical noise even after bouncing - I thought that converted it to a wave audio clip.  Melodyne's user manual states "The 'bounce' function (variously known as 'Render to Disk', 'Mixdown', or 'Print to Track') results in your Melodyne edits or sampler output being finalized in an audio file that can then be played back from a simple and resource-sparing audio track instead of the original track.  This makes it possible to remove Melodyne and/or the software sampler from the original track and even delete the original track entirely, thereby economizing on RAM."  In other DAW's the audio track has to be transported into Melodyne for editing. In Sonar X3 it is utilizing ARA integration as a Region FX; I am assuming that there is no "Editor" to removed once it has been bounced. 
 
But is this my misunderstanding - is it still processing the original clips in the background, until I find them and delete them, thereby "removing" the Melodyne editor?  (Freezing did get rid of nearly all the noise, although still a few instances.)

Did you turn off fast bounce in the freeze options?