Extended Compass (80 note) 6 1/2-Octave
Viennese Fortepiano by R. J. Regier

 

SHORTLY before 1830 the wooden framed fortepiano entered its final period of musical significance. Although composite wood/iron frames were common by that time, and action mechanisms based on Sebastian Erard's patent in 1821 for a double-escapement action were being developed, there remained a thriving interest in more traditional Viennese instruments. Conrad Graf (who had his own shop from 1811-1841) and his contemporaries Josef Brodmann (fl. 1800-1828), Ignaz Bösendorfer (who took over Brodmann's shop in 1828), and Nannette Streicher (d. 1833, with the firm continuing under her son, and later her grandson) responded to the evolving metal-framed piano, but maintained the heritage of their respective workshops, by redesigning the framework of their fortepianos. 
This permitted:
 
       string diameters to be increased slightly, increasing the dynamic
       range without threatening structural integrity;

       the compass to be expanded in the treble, from f'''' to g'''';

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Specifications