This set of keyboard itself is USB interface, but you can connect the keyboard to the iPad via a USB adapter. When you use the applications which are compatible with this set of keyboard, the keys you press will be converted to the corresponding music, and broadcast through the iPad.
This keyboard is compatible with the iPad's most famous music software GarageBand, you can also use this set of keyboard to control Animoog. You may concern about: mac dvd to ipad converter. Once these applications support the iOS CoreMIDI framework and are iOS 4.2, microKEY25 can provide good support.
If you want to become a musician, but can not afford expensive instruments, Korg's MIDI keyboard is a good choice for you.