Midi lagging in GP2; works fine in standalone apps

I built a simple Gig Performer rig a few months ago with mostly Pianoteq and VB3 controlled by one keyboard. Everything was fine, great software.

Recently, after not using it for a bit, I copied my gig file, connected a second keyboard, and started to adapt the GP setup for a two-tier rig. I noticed soon that some of the notes played on the original keyboard were lagging – either they would start up to a second late, or they would start on time but end late.

I disconnected the second keyboard, reloaded the original gig file, but it was still lagging. I rebooted the laptop and keyboard, reconnected the USB cables, tried increasing the buffer (although I don’t think it’s an audio issue), and uninstalled some recent programs, but no luck.

Also, I found that if I run either Pianoteq or VB3 as standalone apps, everything is perfect.

I’m sure I did something dumb, but if anyone has any suggestions of what to try next, thanks in advance!

Really you increased the audio buffer?
What is your sample buffer size?

Is one of your keyboards a StudioLogic?
You didn’t really provide us with very much information about your system, making it very hard to diagnose…e.g… what computer, what OS? What audio interfaces? What sample rate? What buffer size (and increasing buffer size will make things worse, not better)

Good point.

The main keyboard (and the only one connected right now) is a Yamaha CP4.

The other keyboard which I connected briefly was a Casio xw-p1.

Audio interface is a focusrite Scarlett 2i2.

Sample rate is 44.1 khz.

Buffer size is normally 128. I increased it to 256 after the problem started (just as a sanity check during troubleshooting), and then lowered it back to 128.

The problem isn’t what I would normally associate with a too-small buffer (audio artifacts), nor the consistent 10-20 ms latency I’d expect from a too-big buffer. Instead, most notes are perfectly responsive, but one of every 5-10 notes either starts sounding 500-1000 ms too late, or starts on time but finishes 500-1000 ms too late. And the audio sounds fine. If that description isn’t clear I can make a little video of it tonight.

The computer is a Dell i7-6500U 2.50GHZ x 4. 8gb ram. OS is windows 10.

How are the keyboards physically connected to the computer? It is very unlikely that this is an internal Gig Performer issue — there’s something wrong somewhere else. If you open the global MIDI monitor, do you see events occasionally arriving late?

If you create a gig file with a single rackspace containing two MIDI In blocks (one for each keyboard) and with each block going to its own VST, do you still get a problem?

Also, are you using VST2 or VST3 plugins?