Latency Issues

The latency with audio on my Surface Pro 3 and using ASIO was playable but not great. The only thing I could do to get better results was use a usb soundcard.

Latency is a direct result of the audio interface and the drivers coupled, less so, with the power of your computer. Assuming Windows, you need an audio interface that supports ASIO with their own drivers. RME, MOTU, Lynx and others offer low latency interfaces. If you are using the onboard sound of your motherboard, you "might" be able to use ASIO4ALL as an alternative. No where near the best solution but sometimes workable.  If you want the lowest latency my suggestion is RME or Lynx followed closely by MOTU.

I had similar issues with a Surface Pro4.  I could not fix my latency by any combination of Surface, Windows, or Pianoteq adjustments.

At the advice of Didier Martini on this forum, I bought a Steinberg UR-22 Mk II.  It completely cured my latency issues, gave me a sturdier speaker output than the mini phone jack on the opposite side of the USB and power on the Surface, and gave me an easily turntable volume knob on the from of the Steinberg.  And it comes with Cubase AI.

Totally worthwhile.

In the photo, the Steinberg unit is on the top right of the piano:

https://goo.gl/photos/o97pVdM6ZgT179jK6

I have my keyboard (the piano with QRS Sensor Rail) plugged into the MIDI ports on the back of the UR22.  My monitor speakers are also plugged into the UR22 by 1/4" phone plugs.  Then the UR22 plugs into the Surface by USB.  You can optionally add headphones and/or a microphone and/or an electric guitar to the front of the UR22.

That's it.  Simple, and it works.

That's good to know as I just ordered a surface pro 4 for travel practice with Pianoteq (I think I will go for the Acuna 73 as the masterkeyboard, which seems like the best action/weight/size/price compromise). I already have the Steinberg interface for my home PC and it is excellent...(USD powered as well)...

if you have an i-CPU you should be fine with Pianoteq in standalone anyways.
on my SP3 /Win10 / i5 / 8 GB Pianoteq is quite playable (128 samples audio buffer, 64 voices) using the on-board soundcard. Will have a look at the UR 22MKII myself, however. For higher samplerates and for using it in a VST environment.

Best

Try 64 voices, not auto. Also try lowering the sample rate a bit.

I remembered something I had to do on my Surface Pro 3 to fix audio glitches. I assume SP4 is the same. These devices have advanced power management schemes, and in the Control Panel -> Power Options, I could only see a "Balanced" scheme, and no "High Performance" option as I would usually use for audio applications. But the balanced scheme throttles the CPU. You could see the CPU frequency constantly changing in the Pianoteq -> Options -> Perf screen.

After some messing around, I found a way to force the SP3 into solid high performance using the "powercfg" command. You can try this by running (Windows + R) the following command: "powercfg /s SCHEME_MIN" (this means minimum power management, ie max power)

You should now see a "High Performance" option in the Power Options that should be selected as the current scheme. The CPU frequency in Pianoteq should be constant.

My performance factors:
Balanced = 23
High Performance = 39

Unfortunately, this power option doesn't show up if you select Balanced again. It is automatically hidden! The way round this is to duplicate the scheme as a custom one, but that involves a bunch more (ugly) powercfg commands. Try the above first, and let us know if it works.

Interestingly, it seems to be the CPU switching that caused the glitches more than the actual power level. With further experimentation, I was able to create a power scheme that throttled the CPU to a constant 50% power, and it worked fine. This could be useful if you're running on batteries and want to prolong the life.

Thanks all for the suggestions.

I set the max voices to 64 and can now practice my Scriabin preludes with quasi constant pedal and lots of leaps without any noticeable cuts. It's strange that I never seem to get more than 30 voices though, whatever the setting (even in 'auto pessimistic'), but the max is what seems to count for drop outs...
I did have to turn off 'cpu surcharge detection' to avoid cuts totally though. Let the thing burn down if it must!

On my tablet SP4 the CPU speed is constant in 'perf' (at 2390mhz), so I think I will not try to tweak this. There is an "eco' mode which I always switch off when playing, perhaps that's enough. There are very few options anyway in 'power management' that look useful in windows 10 (I found nothing on cpu power).