From Native Instruments:
For best performance, we recommend downloading and installing our new KONTAKT PLAYER 4 to run AKOUSTIK or ELEKTRIK PIANO on current systems. This is particularly important if you are running Pro Tools, you will get much better performance in this host by using our new player.
You can download it from here:
http://www.native-instruments.com/#/...ontakt-player/
Once installed, click the 'Libraries' tab at top left and then select your 'Akoustik Piano Library' or 'Elektrik Piano Library' folder to make these libraries available in KONTAKT PLAYER 4.