Did you watch Tavis Smiley on PBS?

It was about LA Conductor Gustavo Dudamel. During the program Smiley twice referred to a rehearsal session of a very difficult Messiaen piece. I am just becoming "acquainted" with Messiaen and was wondering if anyone saw the program, do you know what piece Smiley was referring to? If you did not see the program how about an educated guess? I was unable to hear enough of the piece (they played just a short clip of the rehearsal) to find it on youtube. Thanks in advance for your help.