Cordepiano is a musical instrument invented by Sergey BelimovCordepiano is a musical instrument invented by Sergey Belimov in 1996 and patented in France and Russia.
In the core of its sound lies the interaction of special string resonators. Generally speaking, they could be strings of any existing instruments – a harp, a cello, or, for instance, Arabic rhebab or Chinese erhu.
Modern piano (a grand piano with its horizontal strings, but not an upright piano) presents the most perspective prime model, as its existing mechanism of key-to-string interaction can be used to move resonators along the strings. The generated sound is made up of the combination of simultaneous soundings: the string, on the one hand, and the resonator, on the other.
Timbre and agogic characteristics of the sound depend on the speed of movement, direction of movement, pressure, presence or absence of additional vibration of the used device (object) between its friction and resonating parts and the string of a musical instrument. 
Cordepiano technique allows for “prolonging” the sound as well as conscious control over its numerous characteristics: attack, fading, internal dynamics and types of vibration, it also gives way to changing timbre/ tone quality of the sounds, using microintervals, playing with multiple sounds.
One may say that modern computer technologies can be used to perform electronic-sensor contact or contactless types of interaction between the key and the device affecting the string, but cordepiano is not an electronic musical instrument. This is the first in the world, unique acoustic instrument which lets a composer work with the sound at the level of its microstructure.
Historically, John Cage’s “prepared piano”, in which the piano sound is combined with percussion sound effect” can be considered to be the predecessor of cordepiano. However, whereas the sound of “prepared piano” remains discreet and newborn timbre is unchanged in the process of performance, cordepiano technique enriches the sound with a possibility to continue and allows for its transformation along the way.