Neither side offered a timeline beyond stating that the negotiations would continue past midnight.
"The conversations will continue past midnight tonight, and the media blackout is still in place," said Louise Sciannameo, vice president for public affairs.
"The parties have agreed to continue meeting beyond the expiration of the contract this evening. The musicians have also agreed to continue the media blackout," said bassist Micah Howard, chairman of the musicians' committee.
The orchestra's next concerts, a pops program featuring the music of John Williams, are scheduled to take place the weekend of Sept. 30 at Heinz Hall.
The musicians are members of Local 60-471 of the American Federation of Musicians.
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