Apple just released a GarageBand update that brings back Alchemy! It's no longer standalone, but for the many fans of this app you can now use it inside of GarageBand at least. There's also a new Audio Recorder in the app! This update also enables AUv3 effects in a new slide-out effects panel.
Thanks to Linda for the heads-up on this!
What's New in GarageBand v2.2:
* The Alchemy synth is available on iPhone 6 or later, iPad Pro, iPad Air 2, and iPad mini 4. ** Requires compatible third-party Audio Unit Extension instruments apps from the App Store.
- Play and record using the new Alchemy Touch Instrument with over 150 synth patches*
- Quickly find Touch Instruments and patches with a redesigned sound browser
- Capture your voice or instrument and apply studio-class effects like pitch correction, distortion and delay with the new Audio Recorder
- Use new mixing effects, including Visual EQ, Bitcrusher, and Overdrive
- Add third-party effects using Audio Unit Extensions**
- Record multiple times over any song section and choose your favorite using Multi-Take Recording
- Perform with Chord Strips from any keyboard instrument
- Add comments or lyric ideas to your song with an integrated notepad
- Remotely add new tracks to your Logic Pro X project from your iPhone or iPad via iCloud
- Stability improvements and bug fixes
At the bottom of the release notes is a brief mention of Logic Pro X integration. This is made possible with a simultaneous update to Logic today. The way this works is kind of clever. Instead of uploading a whole project file from your Mac to iOS, you just upload a mixed-down track to iCloud. When you are finished working in GarageBand it bounces that back to iCloud and you can reopen it in Logic.