This app works with just about any .SF2 file I've thrown at it, including ones that failed to load in GarageBand on my old MacBook. I love how I can also use MIDI over Wi-Fi, which is great if you don't want to shell out cash for an adapter that directly connects your MIDI controller to your iOS device. One thing I think would make midi Keyboard even better, is if AudioBus support was added, but other than that, I can't ask for much more from this app.