Christ is perfect enough to be always good; and as absolutely and infinitely perfect, is always absolutely and infinitely good.
I think the fact, that we have no Psalms in the New Testament, but a direction to sing them, is very significative of the presence of the Holy Ghost. The Church sings its own—has its own joys, and its own relationships.
Note that the angels, not sang, but shouted for joy at the Creation; then at the birth of Jesus, not then man; and in Rev. 5 the saints praise, the angels celebrating the Lamb outside.