Many generations of piano makers have contributed to the development of the pianoforte. Also Julius Blüthnerhas his share especially with the invention of the Aliquot System. It was patented in 1872 and is responsible till to-day for the warm and romantic sound of the Blüthner instruments.The Aliquot System is a fourth string which is added to each note in the treble. It is however not struck by the hammer but vibrates due to indirect stimulation. These strings enrich the tonal spectrum once the instrument is played forte with a colourful variety of harmonics.
To make it work, precise tuning is essential. In the to-day instruments the strings are tuned in unison with the trichords.