Dubler’s default input is the custom USB mic. However, Dubler also allows you to change the input to allow for some experimental uses. Meaning you can route audio from almost anything into the software and see what results you get.
The input can be changed by accessing the Audio Device Settings, via the cog in the top right. You can then select an alternate Input from the Input Device drop-down menu. This can be a different microphone that you may want to use, an instrument instead of a voice or a virtual audio output
You can route recordings that you’ve already made into Dubler by using an audio routing software such as Soundflower (for Mac). There are few virtual audio outputs you can download so have a google and find what’s best for you