From NYTimes.com [All emphases in the following quoted snippets is mine.]
It was not precisely lip-synching, but pretty close.
The somber, elegiac tones before President Obama’s oath of office at the inauguration on Tuesday came from the instruments of Yo-Yo Ma, Itzhak Perlman and two colleagues. But what the millions on the Mall and watching on television heard was in fact a recording, made two days earlier by the quartet and matched tone for tone by the musicians playing along.
Ah ha! Betrayal! Notice from Mary Katherine Ham at The Weekly Standard,
We were betrayed on Hope Day One. Following in the inauspicious footsteps of Milli Vanilli and Ashlee Simpson before them, the all-star chamber orchestra serenading Barack Obama Tuesday was caught in the act of instrumental lip-syncing.
So why would four supremely talented musicians imitate rock musicians? Why this debasement of honesty? At least the oath of office was not lip-synched. Or else conspiracy theorists would have another reason to question Obama's legitimacy.
Back to the Times piece,
The players and the inauguration organizing committee said the arrangement was necessary because of the extreme cold and wind during Tuesday’s ceremony. The conditions raised the possibility of broken piano strings, cracked instruments and wacky intonation minutes before the president’s swearing in (which had problems of its own).
To be fair, Ms. Ham's piece is somewhat tongue-in-cheek. But what would the hue and cry been if the music had sounded terrible? You know, like the poem?
However we do learn, from MSDNC.com
The Marine Band, the youth choruses and the Navy Band Sea Chanters performed live, Florman said, although Aretha Franklin was accompanied by taped music and voices.
It appears that everyone else performed live and survived.
The temperature hovered around 30 for the ceremony on the Capitol steps, too cold for McGill's clarinet, Ma's cello or Perlman's violin to offer true pitch. But the cold played havoc with the piano, which can't hold tune below 55 degrees for more than two hours, Florman said. The group played at 11:43 a.m., and guests seated near them could hear them as well as the tape made two days earlier.
But again, you can't win. And this is the type of thing Andy Levy was cautioning the right about in his excellent piece.