Alma Redemptoris Mater, quae pervia caeli[Here's a link with the plainchant notation and a midi file]
porta manes, et stella maris, succurre cadenti,
surgere qui curat, populo: tu quae genuisti,
natura mirante, tuum sanctum Genitorem,
Virgo prius ac posterius, Gabrielis ab ore,
sumens illud Ave, peccatorum miserere.
Loving mother of the Redeemer,
gate of heaven, star of the sea,
assist your people who have fallen yet strive to rise again.
To the wonderment of nature you bore your Creator,
Yet remained a virgin after as before.
You who received Gabriel's joyful greeting,
have pity on us poor sinners.
The prayer of Pope John Paul II to the Immacolata.
O God, who by the Immaculate Conception
of the Blessed Virgin Mary,
did prepare a worthy dwelling place for Your Son,
we beseech You that, as by the foreseen death of this, Your Son, You did preserve Her from all stain,
so too You would permit us, purified through Her intercession, to come unto You.
Through the same Lord Jesus Christ, Your Son, who lives and reigns with You in the unity of the Holy Spirit,
God, world without end.
(Prayer for the Novena of the Immaculate Conception)