It’s not a huge list of new features, but they look pretty killer.
New in Logic Pro X 10.4
New Features and Enhancements
Smart Tempo
- Advanced tempo detection lets you automatically combine content together, regardless of their original tempo.
 - Record audio without using a click or drag in an audio file and have the performance define your project tempo.
 - Add any audio file and have it automatically conform to the project tempo.
 
Plug-ins
- ChromaVerb is a sophisticated new algorithmic reverb with a colorful, interactive interface for creating rich acoustic spaces.
 - Space Designer has a new design and a scalable, Retina interface.
 - Step FX adds rhythmic multi-effect processing using 3 powerful step sequencers and an X/Y pad.
 - Phat FX makes your tracks bigger and bolder using 9 effects that add warmth and punch to your sounds.
 - The Vintage EQ Collection provides 3 accurate models of vintage analog EQs from the 1950s to the 1970s.
 - Studio Strings and Studio Horns are deeply sampled, realistic ensemble instruments with custom articulation controls.
 - Mellotron is now available as a standalone instrument plug-in.
 - Retro Synth now offers 18 different filter models.
 
Content
- 2 new Drummers play roots and jazz-influenced brush styles.
 - 2 vintage brush kits for Drum Kit Designer .
 - More than 800 new loops in a variety of instruments and genres.
 - New Visions library for Alchemy adds 150 cinematic presets.
 
Other Enhancements
- You can now undo mixer and plug-in actions.
 - The Files Browser now allows you to bookmark locations for your favorite folders containing samples or projects.
 - In addition to Apple Loops, the Loop Browser now supports looping audio file and can preview them in sync with project tempo.
 - A new universal design for controlling articulations provides a consistent interface for Logic and third-party instruments.
 - Plug-ins: The Direction Mixer plug-in has an updated interface, and offers new functionality.
 - The Audio Track Editor can now be opened as a stand-alone window.
 - Logic now supports the Audio Random Access (ARA) standard.
 - Plug-ins: The Category and Manufacturer sections at the left side of the Plug-in Manager window now scroll independently of one another.
 - Region quantization can now be set from a submenu in the contextual menu opened by right-clicking on a region.
 - There is now a preference to toggle user interface animations on or off.
 - There four new options for the behavior of Replace mode when recording MIDI: Region Erase, Region Punch, Content Erase, Content Punch.
 - Smart Controls and Instrument plug-ins now offer a key switch view for Articulation IDs.
 - Transformer, Transform Window, Environment Faders and Step Editor can now edit MIDI fader events.
 - Logic now supports bouncing files as 32-bit float.
 - Click-holding the Replace button in the Control Bar now brings up new options to set the behavior of replace – Content Erase, Content Punch, Region Erase and Region Punch.
 - There is now an option to have Logic automatically set a new color for each newly created audio, software instrument, or external MIDI track.
 - There is now an option to switch the first automation lane in a track to show the last clicked control.
 - There are now Key Commands for Undo and Redo in plug-in windows.
 - The File Browser and Loop Browser now show a waveform overview and playhead when previewing files and loops.
 - Plug-ins: Plug-in windows offer a new Multilink mode that updates open plug-in windows per insert slot as channel strips are selected.
 - Articulation symbols automatically added to the score based on their note articulation setting are colored blue in the Score.