Easy MIDI — MIDI Controller 4+

This app is truly great for producers on the go, especially when you don't want to drag around a huge MIDI keyboard with you everywhere.

Pros:
-You can have two rows of keys to use for the piano, each with separate octave as well as "first white key" control so it can be set up however you like, and allows for hand arrangements other than C position.
-The "Chords" tab is probably the most interesting because it allows you to predefine chords and map them to numbers, so you can easily build a chord progression and play huge chords without being limited by the number of keys that you can press simultaneously on the keyboard.
-For example, "1" could be mapped to a chord with up to seven notes in various octaves, and "2" could be mapped to more notes, then playing both simultaneously allows you to play
enormous arrangements that wouldn't even be possible with two hands.
-Allows you to use mouse and touchpad input and gestures to control the mod wheel, pitch bend and note velocity

Cons:
-Haven't used it enough to discover very many, but there is no way to make it constantly override keyboard input, so if you were playing notes in an application that doesn't support keyboard MIDI input (Pro Tools!!) and you wanted to tweak your synthesizer's sound, you would have to switch applications back to Easy MIDI in order to test your changes.
-In any case, this is something you would probably use a MIDI controller for, so it's not that big of a deal

All in all, this is a great tool for not just playing notes on the fly, but also for easily mapping and saving chord progressions, so you dont' have to export MIDI files between programs.

I decided to take a chance with this app thinking I'd only lose 15 bucs if it didn't work out. WOW! It turned out to be a fantastic buy!

I've able to compose on my mac keyboard using this app. Extremely useful when using BBC symphony app from Spitfire. It's enables you to use the full range of your Mac keyboard.