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

Cardinal Sean P. O’Malley led the ecumenical service which marks the first time the recognition by the Archdiocese of Boston genocide that killed 1.5 million people.

“It is so important that we do not allow the events of the genocide to slip into oblivion,” said Cardinal O’Malley, addressing nearly 800 people seated on benches.

“The one million and a half of life are not forgotten. . . . One of the fruits of their martyrdom is the accumulation of the love that unites us, “he added.