It is from this period that his Méditation sur le premier prélude de piano de J.-S.Bach, pour violon et piano dates, which was going to bring him long-lasting fame, although in fact he is not really the creator of it. In effect, one day in the sitting room of his future parents-in-law, he nonchalantly improvised a melody on the piano based on the first prelude of Bach's Well-Tempered Clavier. His father-in-law, a violinist, wrote down the melody that Gounod had played twice, transposing it up a fifth, and when the young man came back a few days later, played it for him on the violin and asked him to accompany him at the piano. Gounod, thrilled, thanked him so much that the future father-in-law went one step further, selling the melody to a publisher and soon giving to Gounod the 200 francs in profit!The poem, Vers écrits sur l'album d'une jeune dame by Alphonse de Lamartine, uses the image of a girl leafing through a book and finding the one page that moves her (see this fine translation) as a metaphor for finding love under her fingertips, as it were. One can fairly easily sing Gounod's tune to the French words, and I always think of it when I hear it sung with its Latin text. As a result, it is doubly appropriate that the piece is so often sung at weddings.
But the story does not stop there: a short time later, Gounod was seduced by the voice and shapeliness of one of his young students, a certain Rosalie Jousset. To push his advantage, he glued some lines of Lamartine to the sweet melody, which told the young woman exactly what he was feeling. The girl blushed, her breast beat to a new rhythm, her breath sped up... But Rosalie's mother in turn got riled up by Gounod's lessons and, discovering the manuscript of this song that the teacher had given to her daughter, piously undertook the replacement of the words with the Latin ones of the Ave Maria. Gounod was pleased and decide to adopt this version, and that is how an accidental sentimental song, born out of a simple improvisation, became a worldwide hit, the famous Gounod Ave Maria, known around the world.
Those of you who have played both Bach's prelude and the Gounod accompaniment will know that there is this extra measure of arpeggiation in the middle of Gounod's piece. That bar is not something Gounod composed or added: it is found in one of the manuscripts of the prelude, and in only that one, and Bach scholars now generally agree that Bach did not write it. However, it was included in the 19th-century edition that Gounod knew and played, so there it is.
The audio embedded here is sung by the divine Anna Moffo.