Hello David,
Hauptwerk's audio-CPU meter doesn't show the same thing as as Windows Task Manager's one; it specifically shows how close the system is to an audio glitch occurring with the audio driver that's being used.
If Hauptwerk's audio-CPU meter is going into, or nearly into, the red when few or no pipes are sounding then it indicates that the audio driver/host is calling Hauptwerk too late for Hauptwerk to have enough time left to calculate the audio before the hardware needs to play it (i.e. resulting in a 'buffer under-run'), either because the audio driver isn't performing properly, or because the PC is having underlying hardware/driver timing issues (e.g. DPC latency). The following utilities should help to identify whether the latter is the issue, i.e. whether the PC and its drivers are performing sufficiently well to support real-time low-latency audio:
http://www.resplendence.com/latencymonhttp://www.thesycon.de/eng/latency_check.shtml(Leave them running for a while. The second of them, DPCLat might not be fully accurate on Windows 10, but it still seems broadly to work.)
There are also some documents with more suggestions for troubleshooting PC audio problems here:
https://www.hauptwerk.com/clientuploads/documentation/Tutorials/WindowsOptimizationsAndDiagnostics.pdfhttps://www.cantabilesoftware.com/glitchfree/Anti-virus applications (such as AVG) are system-level processes that potentially can, and unfortunately quite often do, cause audio glitches with any low-latency real-time audio applications (not just Hauptwerk), which is especially likely if your PC has other DPC/hardware/driver performance issues related to accessing its hard-drive/SSD.
If needed, there's a gentleman called Francois Ratte (
http://www.hauptwerkconsultant.com/ ) who provides one-to-one remote assistance services to Hauptwerk users to help troubleshoot and resolve PC issues on a consultancy basis. He's very helpful and knowledgeable.
Hope that helps.
Best regards, Martin.
Hauptwerk software designer/developer, Milan Digital Audio.