Good iPad apps can make the iPad feel not like a device running an app, but like an object that is the app. GarageBand isn’t a musical app running on an iPad. It turns an iPad into a musical instrument. The interfaces for each GarageBand instrument are exquisitely skeuomorphic. Every control — every button, every switch, every slider — is custom designed. The keyboard’s use of the accelerometer to detect how hard you hit the keys seems impossibly accurate for a device that doesn’t have a pressure-sensitive display.