Tempo track warping my audio ?

Hello

According to the manual, adding tempo markers (i.e. changing tempi) in the tempo track should not affect the playback speed of the audio files inside the project. Sadly, not the case …

In my project, I have a simple section for rhythm guitar ending with a long sustained chord. It then jumps to some sort of “spanish-flamenco” solo (on another track). For the transition, I wanted a natural sounding ritardando in the click track, so I did one… starting on the first beat of the last mesure of the rhythm guitar section and slowly decreasing to a somewhat considerable amount in bpm (by a factor of 2) by the end of the mesure. Then it abruptly “jumped” to the initial tempo to start the solo at the correct speed. Using NI guitar Rig for the effects, btw. This will be important later on.

When I started the playback, Cubase’s audio engine did not seem to find this amusing, the audio was warped ! Like pitch shifted…

Then I thought, “Wait a minute, let’s try this some other way”. I created a new project, added an instrument track, made a cheesy organ track made up of a few chords with NI Kontakt, exported the mixdown inside the project, deleted the instrument track and then proceeded to wreak havoc on the tempo track leaving nothing in the project but a simple audio mixdown of the organ track. Nothing happened… So that went well.

So here’s the problem

When I load a simple audio file, Cubase behaves nicely and changing tempi with the tempo markers on the tempo track does not affect audio playback.
When using audio WITH VSTs (as inserts or sends - in my case, guitar track with NI Guitar Rig), something else happens.

So is this a problem with the VST part of Cubase or with NI’s plugins more specifically ? Has anyone else encountered this sort of problem when using plugins and changing tempi inside a project ?

Thanks

Have you explored the relationship between linear and musical time base?

Well, yes… At least I think so.

I’ve read the manual regarding the differences between linear and musical time base, and I don’t remember seeing anything that could explain what is happening in my example.

I did forget to mention that both audio clips (the imported organ chords and the guitar with effects) were in musical time base at the time of the “experiment”.

Has anyone tried to replicate what happened in my project ?

It might have something to do with a delay line that is tempo synced inside the Guitar Rig effects rack. I’ll have to check with that…