What is crucial here, is that it can do real-time audio effects, since e.g. Reaper is one inexpensive possibility and it has a non-expiring demo. Protools can also probably be used, but is overkill for this application. You will then need a platform that speaks ASIO, and as such, probably uses VST effects. If it does not, use ASIO4ALL, which provides an ASIO driver for almost all audio devices. If your sound-card is not an audiophile device, then it probably doesn't come with an ASIO driver although I suggest you check anyway. It works with ASIO drivers for low latency. This method requires two loopback devices.

The problem with VB Audio Cable and Virtual Audio Cable, is they only allow one loopback device with the free version. Thus, the plug-in is not in the driver, but you can still get yer fx by sending sound to the default sound device. the default Windows sound device output, set to a virtual device, and send it to an audio processing application.

Such software creates new virtual send and receive devices that can be used to take e.g. One way to accomplish the same thing although it is not technically what you are asking for, is to use a virtual audio loopback device such as Synchronous Audio Router.

Best virtual audio cable settings