Can you link to a guide, YT video or something? I've never seen it in action. I just see a lot of my apps only get active when they are the front app. Side by s

Can you link to a guide, YT video or something? I've never seen it in action. I just see a lot of my apps only get active when they are the front app. Side by side mixing and and generating sounds like the same direction I want to go when using a modern smart phone.