In 1802 or 1803 the couple, together with their child Franz Carl, born in 1800, settled in Vienna, where the young Dorothea von Ertmann soon came to be appreciated as a highly accomplished pianist. Gifted, well‑trained, and an enthusiastic admirer of Beethoven, the baroness became one of his piano pupils.
For New Year’s Day 1804 Beethoven sent the baroness an artistic reproduction depicting two angels—one holding a lyre, the other a sheet of music and a pencil—together with a greeting card: “To Baroness Ertmann for the New Year 1804, from her friend and admirer Beethoven.” This brief note is the earliest document attesting to the acquaintance between the composer and the baroness.
On 19 March 1804, less than three months after Beethoven had sent his New Year’s greeting, the little Franz Carl von Ertmann, the couple’s only child, died at the age of just over three and a half. Contemporary sources report that Beethoven attempted to console the grieving mother by improvising at length at the piano with incomparable refinement and empathy.
In the Allgemeine Musikalische Zeitung of Leipzig, 7 February 1810, in a detailed and extensive review of the edition of Reichardt’s letters, the reviewer allows himself an ironic remark regarding Reichardt’s enthusiastic praise of Ertmann:
Madame von Ertmann is not only (as is right) preferred to all the female pianists of Vienna, nor merely (as is probably not incorrect) to all the female pianists of the world, but she is even preferred to all pianists whatsoever—and for this Herr Reichardt must take full responsibility!
Baron von Ertmann, who had distinguished himself in the Battle of Aspern (21–22 May 1809) near Vienna against Napoleon and had risen in the ranks of the Austrian army, also took part, on 8 February 1814, in the Battle of the Mincio. On this occasion too, holding the rank of colonel, he played an important role in the fighting. Shortly thereafter, with the return of the Austrians to Milan after the long Napoleonic interval, the baron was promoted to commander of the Deutschmeister Regiment—that is, commander of the Austrian garrison then stationed in Milan.
The Allgemeine Musikalische Zeitung of 24 August 1814 reports news from Milan concerning Ertmann’s husband:
Baron Ertmann, colonel of the Deutschmeister Regiment, currently garrisoned in this city, has recently returned from Vienna in the company of his wife, a pupil of Beethoven. Since it is possible to hear the baroness only in compositions by her illustrious master—works which in Italy are scarcely known and for which it is difficult to find anyone capable of performing them—we admire her not only as an excellent pianist, but in particular for her splendid interpretations of these very pieces.
Some time later, the Allgemeine Musikalische Zeitung of September 1814 reported that the baroness had wasted no time in making “heard pieces by her great master, which in Italy are scarcely known and for which scarcely any performer can be found.” The Ertmanns’ stay in Milan at this time was not permanent: the couple frequently returned to Vienna and also spent extended periods in other locations, since Stephan von Ertmann—often without his wife—had to follow the movements of his regiment (at least until 1824, when, having been promoted once again, he was definitively assigned to Milan).
A further concise confirmation of Ertmann’s excellence as a rigorous and faithful Beethoven interpreter comes from a later memoir (1852), though referring to these years, by Dr. Andreas Bertolini, a friend of Beethoven and his physician from 1806 to 1814: Above all, Beethoven preferred to have his sonatas performed by Madame von Ertmann; he himself no longer liked to play them at that time.
Around mid‑January 1817, at the beginning of a letter to the Viennese publisher Tobias Haslinger, Beethoven specifies the dedication of his last piano sonata:
Circumstances have led me to the following dedication for the new sonata: “Sonata for the pianoforte or Hammerklavier, composed and dedicated to Baroness Dorothea Ertman[n], née Graumann, by L. v. Beethoven.” […] As for the dedication, I beg you to observe the utmost discretion, since I intend it as a surprise.