With all the Force Awakens discussion, this one seems to have slipped under the radar...
I watched CBS' broadcast of the 2015 Kennedy Center Honors on December 29 and was pleasantly surprised to hear Williams' voice in narration of the segment honoring Seiji Ozawa, a very short bit of which can be heard ~52 seconds into this preview video posted on YouTube:
The entire 91-minute broadcast is featured on CBS.com: http://www.cbs.com/shows/kennedy_center_honors/video/3B46BD11-F62B-A68F-C39B-EB54202549BC/the-38th-annual-kennedy-cent