slightly off-topic but I often listen to podcasts while playing video games and I've long wanted a simple device—ideally battery-powered and portable but I'll take what I can get—that takes two audio inputs and produces one audio output, allowing me to crossfade between the two as needed, so I can mix between two audio sources on the fly. does something like this exist, and if so, how expensive is it? I haven't been able to find anything.