In today’s Orange County Register online, I review Gustavo Dudamel, Lang Lang and the Los Angeles Philharmonic in the opening concert of the 90th classical music season at the Hollywood Bowl. Click here to read my review, or pick up a copy of tomorrow’s newspaper.
classical life 
I’ve had many conductors who sang along during rehearsal, but I don’t think I’ve ever performed with one who actually sang along with a performance — even during big choral pieces like Messiahs, Mozart Masses, or Vivaldi Glorias.
It was mostly rhythmic grunting (I can’t think of any other words to describe it), but at least one point he sang one of the melodies in “Pictures” — not the whole thing, but for a little bit.
There are recordings in which you can hear the conductor vocalizing. I recall a Mahler 6 with Barbirolli — he was really into it. I have a Beethoven 4 recording with Marinner in which you can hear the podium creaking.