hi all.When pressed play and make some changes in loop (eg fade in fade out) are very slow to implement, and also the loops from the library are very slow to play, corrects the somewhat self so is the Logic??

Hey there Logic Pro21,

It sounds like you are seeing some odd performance issues with Logic Pro X. I recommend these troubleshooting steps specifically from the following article to help troubleshoot what is happening:

Logic Pro X: Troubleshooting basics

http://support.apple.com/kb/HT5859

Verify that your computer meets the system requirements for Logic Pro X

See Logic Pro X Technical Specifications.

1. Test using the computer's built-in audio hardware
   If you use external audio hardware, try setting Logic Pro X to use the built-in audio hardware on your computer. Choose Logic Pro X > Preferences > Audio from the main menu and click the Devices tab. Choose the built in audio hardware from the Input Device and Output Device pop-up menus. If the issue is resolved using built-in audio, refer to the manufacturer of your audio interface.
2. Start Logic with a different project template
   Sometimes project files can become damaged, causing unexpected behavior in Logic. If you use a template, damage to the template can cause unexpected results with any project subsequently created from it. To create a completely fresh project choose File > New from Template and select Empty Project in the template selector window. Test to see if the issue is resolved in the new project.
   Sometimes, issues with the data in a project can be repaired. Open an affected project and open the Project Information window with the Project Information key command. Click Reorganize Memory to attempt to repair the project. When you reorganize memory, the current project is checked for any signs of damage, structural problems, and unused blocks. If any unused blocks are found, you will be able to remove these, and repair the project. Project memory is also reorganized automatically after saving or opening a project.
3. Delete the user preferences
   You can resolve many issues by restoring Logic Pro X back to its original settings. This will not impact your media files. To reset your Logic Pro X user preference settings to their original state, do the following:
   
   1. In the Finder, choose Go to Folder from the Go menu.
   2. Type ~/Library/Preferences in the "Go to the folder" field.
   3. Press the Go button.
   4. Remove the com.apple.logic10.plist file from the Preferences folder. Note that if you have programmed any custom key commands, this will reset them to the defaults. You may wish to export your custom key command as a preset before performing this step. See the Logic Pro X User Manual for details on how to do this. If you are having trouble with a control surface in Logic Pro X, then you may also wish to delete the com.apple.logic.pro.cs file from the preferences folder.
   5. If you have upgraded from an earlier version of Logic Pro, you should also remove~/Library/Preferences/Logic/com.apple.logic.pro.
   6. Restart the computer.
4. Isolate an issue by using another user account
   For more information see Isolating an issue by using another user account.
5. Reinstall Logic Pro X
   Another approach you might consider is reinstalling Logic Pro X. To do this effectively, you need to remove the application, then reinstall Logic Pro X. You don't have to remove everything that was installed with Logic Pro X. Follow the steps below to completely reinstall a fresh copy of Logic Pro X.
   1. In the Finder, choose Applications from the Go menu.
   2. Locate the Logic Pro X application and drag it to the trash.
   3. Open the Mac App Store
   4. Click the Purchases button in the Mac App Store toolbar.
   5. Sign in to the Mac App Store using the Apple ID you first used to purchase Logic Pro X.
   6. Look for Logic Pro X in the list of purchased applications in the App Store. If you don't see Logic Pro X in the list, make sure it's not hidden. See Mac App Store: Hiding and unhiding purchases for more information.
   7. Click Install to download and install Logic Pro X.

Thank you for using Apple Support Communities.

Cheers,

Sterling