Sidecar is the new iOS 13/macOS Catalina feature that lets you use an iPad as an extra display for your Mac. But it also lets you send any app off to your iPad. Then you can wander off and use that app on the iPad, pretty much independently, with the Apple Pencil.
This means you can use some high-level Mac music apps, like Logic Pro X and Ableton Live, on the iPad. There are a couple of catches, but it’s easy to use. In fact, Sidecar is so good that using Mac apps on the iPad like this is actually a viable, sensible option. It’s not just a neat trick that you’ll use once and then forget about.