I'm running Sonar X3 with several instances of the Kontakt 5 VST (9 or 10) as well as a few other VSTs (Play, Steam), and I've got my 24GB loaded up reasonably heavily.  I think perfmon says I'm up to about 16 GB. 

Everything is working perfectly.  EXCEPT when I play audio (either VST softsynth or ever just direct from an audio track) during a continual tempo change.  Then I get audio clicks like crazy.  As long as I don't play audio during a tempo change, everything works perfectly.
 
Any ideas what could be going wrong, or what settings I need to be fiddling with?  I'm running Windows 7 on a 2.8 quad core i7 with 24 GB RAM and streaming all my samples off of two SSDs.  Audio interface is an M-Audio Audiophile 24/96 using ASIO drivers.

Any help would be appreciated.   I'm under some tight deadlines to produce some stuff and this is driving me nuts. 

There are some effects, like delays, that follow the host tempo, and when tempo changes, they click when they adjust themselves in the middle of playing audio. The offending effect might be on your track or bus or it might be part of the VSTi setting, so you'll have some detective work. You said it could happen with just audio, so likely a track or bus plugin. It can be fixed by turning off the plugin's "follow host tempo" setting or by using some other effect.

Does the project have tempo-based FX or synth patches in it? A lot of tempo-based VSTs will behave strangely when tempo is changing while notes are sounding. IIRC, the Sonitus Delay is one example of an FX that doesn't play nice with a continuously changing tempo.
 
Musically speaking, "continuous" tempo changes don't really make sense. Ultimately, you should only need one tempo for each note or chord that pertains until the next note or chord.

Thanks for the quick replies.  It does indeed to be a VST issue--one of my Kontakt libraries syncs to tempo and it appears that if you have more than a few instruments loaded from it then it causes problems.  Which is a bummer because I want to use more than a few instruments from it, but at least I know what is causing the problem now.  At worst I can isolate the instruments from that library and record them individually if I need to, then unload them and record everything else. 

Brundlefly, "continuous" tempo changes most definitely make sense "musically speaking".  Have you ever written orchestral music?  Ever heard of an accelerando or a rallentando?

JamieH
Brundlefly, "continuous" tempo changes most definitely make sense "musically speaking".  Have you ever written orchestral music?  Ever heard of an accelerando or a rallentando?

 
Yes. What I'm saying is that all accels/rits/rubato can (and should) be boiled down to one tempo change per note when working in a DAW.

That may be fine if the DAW is the be-all end-all of what you are trying to do.   When parts of what I'm creating is going to go to live players and they're going to use a click-track from it or at least build a click track based off of it, I need to be able to have gradual continual tempo changes over time and have it work.   I'm not even sure what you are referring to by changing the tempo "once per note". I've got an entire orchestra of players here on 100 different midi channels and I'm changing tempo gradually over the course of several measures.  

I've been doing this in Sonar since before it was even called Sonar, so I really don't see what the problem is.   It's always worked just fine.   Obviously certain VSTs don't play nice with it, so I'll have to deal with them specifically.

What I'm getting is that it's not useful to have two or three tempo changes between notes that you can get when you draw a line in the tempo view or insert a series tempos with too fine a step. And it can cause problems like you're encountering. If the ultimate goal is a click track or a conductor's baton beating quarters, any step smaller than that is similarly unnecessary.
 
In any case, it sounds like you know what you want. Not knowing your background and experience level, I just wanted to help you avoid the pitfall I've seen other users fall into of drawing "continuous" lines in the tempo view, thinking that more, smaller  tempo changes will somehow yield a "smoother" change when all it does is cause trouble in various ways.
 
 

I think I see what you are saying--you are saying define the tempo at most once per BEAT, so instead of defining accelerando as a smooth increase from point A to point B you would define it as a series of 1 beat step ups.
 
That would probably work, but would require the click track to be programmed differently than I have done in the past.  It is something to consider if I can't get things to work.

Exactly. The way I'm usually working is by recording a part in real time first with natural tempo variations, and then using Set Measure/Beat At Now to tell SONAR where the beats are and let it set the tempo for that segment. When tempo is changing quickly, I might set 8th notes, but the main point is I never set a tempo where there's no note.

I agree completely with the tempo change @ note approach. Quantize the tempo track!
However, that won't prevent clicks from effects that have live audio running through them at the point of a beat.