Scaler 2.7.1 crashes DAW when using scale selection command in multiple Scaler instances


I have just bought Scaler2 (v2.7.1 at the moment) and I am experiencing very frequent DAW crashes under the following circumstances:

  • Windows 11
  • Scaler2 v2.7.1 VST3 64 bit (I think it also happened to me when trying the VST2)
  • Host: Reaper 6.71 64bit or Cubase Pro 12, happens in both
  • Creating two instances of Scaler 2 in the same project
  • Defining (in each instance) two “Scale selection” commands (for example C Major using CC20 and C Minor using CC21)

Then if I start changing from C Major to C Minor repeatedly (both instances changing at the same time as I have defined the same scale selection commands in both), all seems to work fine but after a number of changes to the scale, the whole DAW suddenly crashes without explanation.

This is easy to reproduce, just create the above conditions and then quickly send CC20 and CC21 commands until it crashes.

When I load only one Scaler2 instance, this issue does not happen. So it looks like there is some strange interference between Scaler2 instances, even if you don’t use the Sync options.

I hope you can replicate this. Thanks!

By the way, an important note: the behavior seems different when the GUI is closed compared when the GUI is shown.

To replicate please make sure the GUI for both Scaler2 instances is open at the same time before sending repeated CC20 and CC21 to change scale from C major to C minor and vice versa. That’s how I replicated it.

Welcome. Sorry to hear this. I’ve not updated Scaler to v2.7.1 so I can’t speak to the issue. I may find time to try to replicate. When you say “send quickly” – what rate, just a fast toggle or are these are CC 20 and CC 21 embedded in a track?

Anyway, don’t bother answering for now. Some know much more about this than I do. Sounds odd. I’ve not heard this mentioned before.

Hi @DavidBluecame

thanks for the detailed reporting, we will try to replicate it and get back to you.

Hello, thank you both for your replies!

To replicate, you can send the CC20 / CC21 events 2-3 times a second repeatedly until it crashes.

In real life situations you don’t send those events so quickly, but still crashes randomly. I sent the events quickly (2-3 times a second) just to force it to happen.

Thanks and best regards.

I have found that when using midi CC to recall performancees I need to trigger them just before the bar that I want the performance to start (say 1/32 when playing T 120 BPM). Because of this I think that there may be some issues around Scaler responding to these commands, although the issues may be DAW related or even hardware related (cpu and time to load the appropriate performance from disc) or a combination of all these?

suggests that this may be related to hardware being able to process all the commands.

Having said that I have created a small project in Ableton Live that uses CC20 and CC21 to switch between two performances which seems to work. But on my project I am switching every 4 bars = 16 secs approx.


I have a similar issue when using multiple synced Scaler instances in a project. As I found out, the crash does not occur when I turn off OpenGL rendering with the ScalerSettings App. It would be interesting, if turning off OpenGL rendering also fixes the problem in your situation.

See here for ScalerSettings App:

My assumption as a software developer is, that when multiple Scaler windows are open, they try to update their window content at the same time when receiving the midi CC commands resulting in a crash, maybe because of some shared OpenGL resource.

The same could be the case when multiple Scaler instances are synced.