Crystal Synth XT features MIDI keyboard input via Apple's camera adapter and sharing of sounds with the desktop version of Crystal.
However, on the iPhone you can still browse sounds, play notes from the keypad, create new sounds with the Breed feature, modify patches with the Design feature, and share sounds with desktop Crystal VST.
With patch sharing you can create sounds on your iPad or iPhone while away from the studio, then transfer them to the desktop Crystal when you get back to the studio to use in recording projects.
With MIDI keyboard input, you can connect a MIDI keyboard to your iPad or iPhone and play Crystal Synth XT like a hardware synth.
Or, create banks of sounds on the desktop Crystal, then transfer them to the iPad/iPhone Crystal to use in a live performance for a truly portable rig.