Duet for Two Sopranos, “Ach, was müssen wir erfahren?” (fragment), K. 43a
par Wolfgang Amadeus Mozart
Mozart’s “Ach, was müssen wir erfahren?” (K. 43a) is a short, fragmentary duet for two sopranos written in Vienna in October 1767, when the composer was just eleven. Surviving without accompaniment and without an identifiable dramatic destination, it offers a rare glimpse of Mozart’s youthful response to a specific moment of public grief amid the city’s smallpox epidemic.
What Is Known
The fragment “Ach, was müssen wir erfahren?” (K. 43a) survives as an autograph manuscript now in the Bibliothèque nationale de France (Département de la Musique, MS-259) [2]. The New Mozart Edition describes it as a brief duet for two sopranos, written in Vienna in October 1767, and transmitted without accompaniment; its larger dramatic context—whether it belonged to an occasional stage work, a private Singspiel scene, or an isolated ensemble—is not known [3].
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The anonymous German text is associated with mourning during the 1767 smallpox crisis; the New Mozart Edition connects it to news received in Vienna on 15 October 1767 of the death (from smallpox) of Archduchess Maria Josepha [3]. The work is catalogued in the Internationale Stiftung Mozarteum’s Köchel Verzeichnis as K. 43a [1].
Musical Content
What survives is essentially a two-part vocal texture (two soprano lines) with the text underlaid; no instrumental parts are transmitted in the autograph source described by the New Mozart Edition [3]. Even in this reduced state, the fragment suggests Mozart’s early ease with ensemble writing: the voices appear conceived in dialogue rather than as a solo with mere doubling—an embryonic operatic instinct, shaped in the same Vienna period when he was absorbing Italianate vocal style at close range.
[1] Internationale Stiftung Mozarteum: Köchel Verzeichnis entry for K. 43a, “Ach, was müssen wir erfahren!”
[2] Bibliothèque nationale de France (BnF): page noting Mozart autograph manuscript “Ach, was müssen wir erfahren”, 1767, MS-259
[3] Digital Mozart Edition / Neue Mozart-Ausgabe (English preface PDF): discussion of the fragment “Ach, was müssen wir erfahren!” (K. Anh. 24a / K. 43a), including dating, context, and lack of accompaniment