"As loudspeakers played the tape-recorded voices of Franklin D. Roosevelt, John F. Kennedy, Lyndon B. Johnson and Richard M. Nixon, scholars, journalists and curious citizens pondered what presidential tape recordings have already added to history and what still-secret tapes may show, and whether the 18 1/2-minute gap would ever be filled. The hum from the gap was also played."
"At a two-day conference on the tapings, which concluded this afternoon at the Kennedy Library here, John Carlin, archivist of the United States, said it would be several months before experiments on blank tape from the Nixon era would show whether it was worth exposing the erased part of the tape to the risks of restoration by current technology. The erasure on the June 20, 1972, tape, remains one of the great mysteries of the Watergate era. H. R. Haldeman, Nixon's chief of staff, took notes that indicated he and the president had discussed Watergate in the June 20 meeting, just three days after the burglary." (from The New York Times)