After the death of her husband Constanze contacted Johann Anton André, the publisher of Mozart’s compositions. During her marriage to Wolfgang Amadeus Mozart she had given birth to six children but only two survived – Carl Thomas and Franz Xaver Wolfgang – and they soon began to show they had a natural gift for music. Carl Thomas first completed a business apprenticeship in Livorno and then, with the help of Joseph Haydn, a great admirer of his father, turned his attention to studying music. However, in 1810 he abandoned his studies to take up a career as a civil servant. His younger brother Franz Xaver Wolfgang, known as W. A. Mozart (jr.), took music lessons from Johann Nepomuk Hummel, Georg Joseph Vogler, Antonio Salieri as well as Johann Georg Albrechtsberger and became a composer of some importance and a pianist.
In 1809 Constanze Mozart married the Danish diplomat Georg Nikolaus Nissen, who, besides historian and librarian Friedrich von Schlichtegroll, was one of Mozart’s first biographers.
In the second half of the 19th century there was increasing academic interest in Wolfgang Amadeus Mozart’s œuvre. The first edition of a “Chronological and Thematic Catalogue of all Compositions by Wolfgang Amadé Mozart”, the so-called Köchel-Verzeichnis was edited by Ludwig Ritter von Köchel and published by Breitkopf & Härtel in Leipzig in 1862. The International Mozarteum Foundation started the Old Mozart Edition, the publication of all Mozart’s works in 1877, a project which continued until 1910. The New Mozart Edition was begun in 1955 at the instigation of the International Mozarteum Foundation and published by Bärenreiter in Kassel. The main body of this mammoth publishing project was completed in 1991.
Since 2007, the focus of the scientific division of the Mozarteum Salzburg Foundation has been directly specifically at the Digital Mozart Edition: All compositions are therewith being made freely accessible to Mozart fans and scientists throughout the world via the Internet, in the form of notes and audio files.