iPad App Review: Korg iMS-20
The Korg MS-20 is one of my favourite analog synths of all time. I have the Korg Legacy Bundle with the (now discontinued) 3/4 sized USB Contoller modelled after the original and it is always within reach.
iPad controllers Review: Midi Katapult
Download the trial version for free but up until you buy the license via PayPal for around ¥3000 it runs for 30 minutes at a time before it locks up and then you have to reload it to start afresh