So did she lip-sync or didn't she?
"Regarding Ms. Knowles-Carter's vocal performance," USMC spokesman Capt. Eric Flanagan said in a statement, using the singer's full last name, "no one in the Marine Band is in a position to assess whether it was live or pre-recorded."
He confirmed the Marine Band itself did not perform live, saying because there was no opportunity for Beyonce to rehearse with it, "it was determined that a live performance by the band was ill-advised for such a high-profile event."
The singer's representatives did not respond to requests for comment.
Marine Band spokeswoman Master Sgt. Kristin duBois had told several media outlets that event organizers ordered band director Col. Michael J. Colburn to switch to a backing track -- customarily prerecorded in case of bad weather -- shortly before Beyonce performed.
Col. Colburn told NBC News singers and the band make the decision about whether to perform live, sometimes on inauguration day. He said Beyonce had been busy preparing for her Super Bowl halftime show and had no time to rehearse the song properly with the Marine Band.
Kelly Clarkson's representative told The Associated Press that Clarkson performed "My Country, 'Tis of Thee" live at Monday's ceremony. James Taylor had earlier performed a live acoustic version of "America the Beautiful."
It is not unusual for performers at events to lip-sync to live or recorded music.
Jennifer Hudson lip-synced the national anthem and Faith Hill did likewise with "America the Beautiful" at Super Bowl XLIII in 2009, at the directive of pregame show producer Rickey Minor. Whitney Houston lip-synced the anthem at the 1991 game.