CHICAGO (CBS) — Chicago Symphony Orchestra musicians have rejected the “last, best and final offer” from CSO management, nearly a month after going out on strike.

“We are extremely disappointed that management refuses to hear the Musicians’ concerns about a secure retirement for the Musicians and a secure future for the CSO”, Chicago Federation of Musicians negotiating committee chairman Steve Lester said in a statement Monday night. “In contrast, the proposal put forth by the Union – but rejected by the Board — fully addressed management’s alleged concerns about unpredictable pension funding while guaranteeing the Musicians and the Orchestra the security deserved.”

The musicians have been on strike since March 10, and the CSO has cancelled several scheduled concerts over the past four weeks.

The Chicago Symphony Orchestra Association said it is now reviewing the CSO season schedule, and will need to cancel additional concerts as the strike continues.

“Throughout these negotiations we have continued to listen to the concerns of our musicians and have directly responded with proposals that provide an exceptional, comprehensive compensation package. With the final offer on Sunday night, we have proposed a long-term agreement that would allow the parties to repair their working relationship, bring stability to the organization, support the musicians in a transition to a new retirement benefit and grow the annual base salary by 12%, retaining a contract that remains at the top of our industry,” said CSOA President Jeff Alexander.

Management has said the latest offer included a 5-year agreement instead of a 3-year deal, higher annual salary increases, the most guaranteed time off at 12 weeks per year and the highest seniority pay of any U.S. orchestra, starting with 10 years of service.

The musicians have said management’s latest contract offer would leave their salaries behind other major orchestras in Los Angeles and San Francisco, and would deny most musicians any guaranteed increases in pension benefits.

Management had been seeking to switch from a defined benefit pension plan to a defined contribution plan.

The musicians plan their next free concert for April 15, at 7:30 p.m., at the Apostolic Church of God, 6320 S. Dorchester Av.

Anyone who plans to attend must register at CSOApostolic.eventbrite.com.