Breitkopf & Härtel is a German music publishing house. The catalog currently contains over 1,000 composers, 8,000 works, and 15,000 music editions or books on music. The name “Härtel” was added when Gottfried Christoph Härtel took over the company in 1795. In 1807, Härtel began to manufacture pianos, an endeavor that lasted until 1870. The Breitkopf pianos were highly esteemed in the 19th century by pianists like Franz Liszt and Clara Schumann.
In the 19th century, the company was for many years the publisher of the Allgemeine musikalische Zeitung, an influential music journal.
The company has consistently supported contemporary composers and had a close editorial collaboration with Beethoven, Haydn, Mendelssohn, Schumann, Chopin, Liszt, Wagner, and Brahms. In the 19th century, they also published the first “complete works” editions of various composers, for instance, Bach (the Bach-Gesellschaft edition), Mozart (the Alte Mozart-Ausgabe), and Schubert (the Franz Schubert’s Werke). This tradition continues today with prominent contemporary composers.
According to Wikipedia