I was reading Dom Johner's Chants of the Vatican Gradual (available on Musica Sacra here) this morning and was completely captivated by his explanations of this Sunday's propers. The usually sober and restrained author gets quite carried away. These excerpts are just too good to keep to oneself:

Introit: Today, however, our song tells of a power which sweeps everything before it, of a force which nothing can withstand. There is a feeling of mystery about its low-pitched beginning. But then the melody expands with tempestuous speed, expands until it fills the entire earth. But it is no devastating hurricane, breaking the nations as a reed and making poor humanity cry out in despair. It rather resembles a storm of spring, imparting new strength to an aging world, from which new creations rise: the marvel of the Catholic Church, the phenomenon of holiness on the sinful earth, the prodigy which bears God in its heart as the sweet guest of the soul. Hence, in spite of all its impetuosity and power, this song is extremely pleasant to our musical sense . . . Whoever lives himself into this song seems to feel that the Spirit of the Lord filled also the heart of the composer and bestowed upon him this power of song. May the Holy Ghost likewise fill our hearts, that our chant may penetrate into the hearts of the faithful like Pentecostal grace!

Second Alleluia: This melody must be numbered among the most impressive and most beautiful in the entire Graduale. "Here all kneel"—that is the simple rubric. And when at high Mass the bishop with his assistants kneel down at the throne, when all those in choir bend the knee, then this one wish is uppermost: Would that I might sing this chant with that deep fervor with which it was first conceived and then sung throughout the centuries, with that depth and ardor with which the Blessed Virgin called upon the Holy Ghost during the novena preceding Pentecost Day! Like the dew from heaven its tones should sink into the hearts of the faithful.

Sequence: The composer of this song was a veritable harp of God, on which the Holy Ghost Himself played. Its tones will continue as long as mankind looks up in heartfelt prayer to the "Father of the poor." Whoever realizes the neediness of his own heart, whoever can sympathize with all that moves the heart of his fellow man, whoever reflects while he peruses the text and the melodic development, upon the work of the Holy Ghost in souls and in the Church, will of his own accord arrive at the rendition which is most suitable for this magnificent song.

Communio: In most Masses the Ite missa est harks back to the melody of the Kyrie. In a similar way this Communion reminds us of the festive enthusiasm of the Introit. With striking clearness it portrays in the first phrase the sudden coming of the Holy Ghost. One seems actually to hear the mighty wind in the recurring fifths and the ascent to f1 with its interval of a fourth. That is word-painting which, although it violently urges us along, is nevertheless enjoyable. In spite of all His might and power, the Spirit who comes is the Spirit of order, of life, and of love. . . . "In a certain way, the miracle of Pentecost becomes visible in Holy Communion. The Holy Ghost, it is true, does not come in the form of fiery tongues, but in the form of bread He enters into our hearts; for Christ is filled with the Holy Ghost. And although the species disintegrate, the Paraclete wishes to remain with us, to take hold of us spiritually, and fill us with holy enthusiasm" (W.K.).