They are present still! We are not solitary though we seem so. Few now alive understand or sanction us; but those multitudes in primitive time, who believed, and taught, and worshiped as we do, still live unto God, and, in their past deeds and their present voices, cry from the Altar. They animate us by their example; they cheer us by their company; they are on our right hand and our left. Martyrs, Confessors, and the like, high and low, who used the same Creeds, and celebrated the same Mysteries, and preached the same Gospel as we do. And to them were joined, as ages went on, even in fallen times, nay, even now in times of division, fresh and fresh witnesses from the Church below. In the world of spirits there is no difference of parties.
— John Henry Newman, Sermons.
At First Vespers for this great feast is sung Laetamini in Domino. Here is a gorgeous setting by Jean Richafort (c.1480-c.1550), sung by the Huelgas Ensemble.
Laetamini in Domino, et exsultate justi. Et gloriamini, omnes recti corde.
Be glad in the Lord, and rejoice, ye righteous: and shout for joy, all ye that are upright in heart.
At Mass the Gradual is Timete Dominum. Here is the chant, and below is a recording sung by A Sei Voci. (You now have everything you need to sing it yourself.)
Revere the Lord, all you saints of his; for there is no want among those who fear him. Those who seek the Lord shall lack no good thing.
Happy Feast of All Saints!