@falktx I just overhauled PortAudio's CMake support https://github.com/PortAudio/portaudio/pull/443 I remembered JACK is cross platform so the check to enable the JACK host API is not guarded by any checks for the OS. So what if you built PortAudio with the JACK backend on Windows and told JACK to output to the JACK PortAudio backend? 😆 I think it would end up as a roundabout way to have an application output as a JACK source without connecting it to a hardware output.