The Chicago Symphony Orchestra says it agreed Sunday to a three-year contract with its musicians union on a deal to replace the agreement that expires Sunday.

The deal must be ratified by the CSO board of trustees and the orchestra members in the Chicago Federation of Musicians.

CSO musicians struck for two days in September 2012 and for seven weeks March and April of 2019 before agreeing to a contract calling for a 13.25% wage increase over five years.

The CSO said details of the new deal will be released after ratification.

Music director emeritus for life Riccardo Muti leads the CSO season-opening concert on Sept. 21 at Orchestra Hall and will take the orchestra to New York to open Carnegie Hall’s season on Oct.