T.M. Moore passes on this quote from Basil’s homily on Psalm 1:
A psalm is the tranquility of souls, the arbitor of peace, restraining the disorder and turbulence of thoughts, for it softens the passion of the soul and moderates its unruliness. A psalm forms friendships, unites the divided, mediates between enemies. For who can still consider him and enemy with whom he has sent forth one voice to God? So that the singing of psalms brings love, the greatest of good things, contriving harmony like some bond of union and uniting the people in the symphony of a single choir.