For many years, following the second Pesach seder the Rebbe would conduct a farbrengen. On these occasions, the Rebbe would discuss portions of the Haggadah. In the course of this farbrengen in 5715, the Rebbe declared, “I do not know why at the seder tonight the Haggadah was recited with such melancholy and lowness of spirit. Let us, therefore, sing the joyous melody of Vehi Sheamdah.”
The crowd did not know the tune the Rebbe was referring to, so the Rebbe sang it several times, until the assembled began to sing it together with the Rebbe.
וְהִיא שֶׁעָמְדָה לַאֲבוֹתֵינוּ וְלָנוּ שֶׁלֹּא אֶחָד בִּלְבָד עָמַד עָלֵינוּ לְכַלּוֹתֵנוּ. אֶלָּא שֶׁבְּכָל דּוֹר וָדוֹר עוֹמְדִים עָלֵינוּ לְכַלּוֹתֵנוּ. וְהַקָּדוֹשׁ בָּרוּךְ הוּא מַצִּילֵנוּ מִיָּדָם
And this has stood by our fathers and us. For not just one rose against us to annihilate us. But in every generation there are those who rise to annihilate us. And the Holy One, blessed be He, saves us from their hands.