Blüthner and the Aliquot Fourth String System

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Generations of piano makers have been constantly attempting to improve the quality of their instruments. Julius Blthner made an important contribution with the development of the Aliquot System. Patented for the first time in 1872, it was one more step that provided Blthners well known warm and romantic sound. The patented Blthner Aliquot System consists of an additional fourth string in the treble section which is not struck by the hammer. The fourth string vibrates by resonance, and introduces additional overtones which enrich the dynamic sound.

Does it work?
Many people are sceptical, but it is easy to test. Simply play a note alternately muting and then leaving the fourth string to vibrate.
It is surprising how loud the Aliquot string is even though it has not been struck by the hammer. Currently, the Patented Aliquot System employs an additional fourth string in the treble section attached directly to the bridge that is not struck by the hammers.
The fourth string is stimulated to vibrate through sympathetic resonance when the other three strings are struck, which results in an acoustical system enriching the overtone spectrum. It produces a very dynamic sound, which is audible over a wide range. This unique effect conveys the resonant treble of the Blthner piano. As an example, it is possible to experience this special effect in many piano compositions giving an added dimension in tone colour and dynamics. Another factor that is that all Blthner strings are individually hitched. For optimum effect, precise tuning is essential. In todays instruments the aliquot strings are tuned in unison with the trichords.