The soft sound of the duduk, the national instrument of Armenia, enveloped the Cathedral of the Holy Cross Saturday afternoon at the start of a prayer service held on the eve of the 101st anniversary of the Armenian genocide.

Cardinal Sean P. O’Malley led the ecumenical service that marked the first time the Archdiocese of Boston has formally commemorated the genocide that killed 1.5 million people.

O’Malley was joined by church leaders representing a number of Catholic, eastern Orthodox, Christian, and Armenian churches across the eastern United States and Canada.