Beginning Monday morning, the Chicago Symphony Orchestra will put down their instruments in favor of picket signs, as the musicians will officially go on strike.

According to a press release issued by the Chicago Federation of Musicians, the musicians walked out of negotiations with the Board of Trustees and announced that they would not return to work until a new contract agreement is reached.

“We have been clear from the beginning that we will not accept a contract that diminishes the well-being of members or imperils the future of the orchestra,” Steve Lester, the Chair of the Musicians of the CSO negotiating committee, said in a statement.

The press release says that the Board of Trustees has presented the orchestra with a reduced benefits package, which includes an end to pension stipends of $3,000 per year for orchestra members after they retire.

According to the Chicago Classical Review, the management proposal to the musicians represented a 5 percent increase in base pay over the life of the new three-year contract, and said that it would shift musicians from a pension plan to a direct contribution plan.

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The management group says that continuing the pension plan would “endanger the financial health of the institution,” according to a letter detailing the proposal that the group published.

After rejecting the offer, the musicians of the orchestra will picket outside of the building beginning at 8 a.m. Monday morning, and will not perform until a new contract is reached.