Key driving apparatus and keyboard musical instrument

A keyboard musical instrument comprising:

• a keyboard having keys;
• a music performance information generator configured to generate music data for automatic music performance;
• a key driving controller coupled to the music performance information generator to receive the music data from the music performance information generator;
• the key driving controller being configured to generate a key driving control signal based on the music data and generate a first control voltage based on the key driving control signal;
• and
• a key driving apparatus coupled to the key driving controller to receive the first control voltage from the key driving controller,
• the key driving apparatus comprising:
• a first elastically deformable unit configured to receive the first control voltage,
• the first elastically deformable unit being configured to show elastic deformations of stretch and shrinkage based on a level of the first control voltage, and
• the first elastically deformable unit being configured to allow the key to be driven by the elastic deformations of stretch and shrinkage of the first elastically deformable unit,
• the first elastically deformable unit comprising:
• electrodes configured to receive the first voltage;
• and
• an elastically deformable polymer film having a dielectric property, the elastically deformable polymer film being interposed between the electrodes, the elastically deformable polymer film being configured to show elastic deformations of stretch and shrinkage based on the level of the first control voltage, the elastic deformations being such that the elastically deformable polymer is stretched in an in-plane direction and shrunken in a thickness direction at a first level of a control voltage, and that the elastically deformable polymer is shrunken in the in-plane direction and stretched in the thickness direction at a second level of the control voltage.