Liszt was in the bloom of youth and of rising fame when he made the acquaintance of the woman to whom his life was to be linked for ten years. The only love affair that produced children (Blandine, Cosima, Daniel). D’Agoult and Liszt met in 1833 at a musical gathering hosted by Marquise Le Vayer. The chemistry was unmistakable. Marie was six years older than the young enchanter, and by the early summer of 1833 their affair was in full bloom.
Liszt visited her in Croissy, and Marie came to Paris where they secretly met in a small apartment affectionately referred to as the “rat hole.” Such was the woman who, captivated by the youth and talent of the Hungarian virtuoso, abandoned for him husband and child, and, sacrificing position, reputation and fortune to her passion, was for ten years the faithful companion of his travels all over Europe.
Following the tragic death of her daughter Louise, Marie d’Agoult found herself pregnant with Franz Liszt’s child. Since she was still married to Charles d’Agoult, it was impossible to stay in Paris. She wrote her husband in May 1835, telling him that their marriage was over. In order to avoid the scandal, which was hardly possible, the lovers made secret arrangements to elope to Switzerland. Parisian society was dumbfounded that a very prominent and beautiful Comtesse should leave her husband for a traveling pianist, and in the public eye the whole affair was branded a flagrant case of abduction. Nevertheless, the couple left for Basle and since Charles d’Agoult had obtained a legal separation from his wife.
She became close to Liszt's circle of friends, including Frédéric Chopin, who dedicated his 12 Études, Op. 25 to her (his earlier set of 12 Études, Op. 10 had been dedicated to Liszt).
Liszt's "Die Lorelei," one of his very first songs, based on text by Heinrich Heine, was also dedicated to her. D'Agoult had three children with Liszt; however, she and Liszt did not marry, maintaining their independent views and other differences while Liszt was busy composing and touring throughout Europe.
The two left Paris for Switzerland in May of that year. Took a trip to Italy in 1837 as an established couple. Also visited George Sand at her home. Both Blandine and Cosima were quietly born out of the country under fabricated birth certificates. 1838, Suttoni claims is the beginning of the end of their relationship (on happy terms, anyway). Daniel was born in May 1839, in November of that year Liszt would embark on a series of performance tours throughout Europe. Touring and absences led to the final end of their relationship in 1844.
Besides many critical contributions on music, painting and sculpture, the Countess tried her hand at political economy and philosophy. In 1845, just about the time she broke off her liaison with Liszt, Madame d'Agoult entered the arena of politics.
Between 1835 and 1836, Liszt composed a collection of pieces entitled “Album d’un voyageur,” which was eventually published in 1842. After some major revisions, the majority of these compositions reappeared in a collection of three suites entitled “Années de pèlerinage.” And the first volume, entitled “Première année: Suisse,” contains a variety of musical, emotional and pictorial impressions from his time spend in Switzerland. Liszt suggested that in this collection “I have tried to portray in music a few of my strongest sensations and most lively impression.”