Audiobus: Use your music apps together.
What is Audiobus? — Audiobus is an award-winning music app for iPhone and iPad which lets you use your other music apps together. Chain effects on your favourite synth, run the output of apps or Audio Units into an app like GarageBand or Loopy, or select a different audio interface output for each app. Route MIDI between apps — drive a synth from a MIDI sequencer, or add an arpeggiator to your MIDI keyboard — or sync with your external MIDI gear. And control your entire setup from a MIDI controller.Download on the App Store
Audiobus is the app that makes the rest of your setup better.
Alchemy presets in Logic Pro
In a couple of the reviews I've seen that all the presets for Alchemy are included, but that seems very much to not be the case AFAIK. In fact quite a few of the presets that are in GarageBand for iOS are not present in Logic.
For example in GB there is a whole section of vocal-like sounds, with presets such as Art Duo, Girls Choir, Cosmic Boys Choir etc... Most of these are missing from Logic.
I've downloaded all the content of course.