# Influence of Piano Key Vibration Level on Players' Perception and Performance in Piano Playing
## 4 Conclusions  
By systematically investigating the players' personal judgment of the instrument quality of the vibration level in the keys, we observed strong integration effects of auditory and tactile information. The results give an illustration of the strong multi-modal effects in piano playing. The subjects perceived differences in the sound of the instrument when the vibration level in the keys was changed. The preference of vibration level \(V_{2}\) over \(V_{3}\) indicates an optimum or a \"sweet spot\" of piano key vibration levels, which depends on the instrument's sound and sound balance. In line with the results of [PERSON] and [PERSON] [8], the vibration levels in this experiment significantly affected the instrument's judged sound quality but not its control and feel. However, in contrast to the design of the present experiment, [PERSON] and [PERSON] [8] reduced the level of the broadband part of piano key vibrations of an acoustic instrument. An interesting direction for future research is to determine the vibration level differences that pianists can differentiate. This would help to understand if an instrument can be identified based on its vibrotactile feedback only, while the instrument's auditory and force feedback are kept constant. Some participants in this experiment perceived a spatial sensation and described it as room or reverb effect on the sound when playing with higher vibration levels (\(V_{2}\), \(V_{3}\)). For several applications it could be interesting to understand the conditions that can cause such an illusion. We did not find systematic differences by analyzing the influence of the vibration levels on the timing and dynamics accuracy of the pianists' musical performances. We can not exclude that such an influence exists but with the proposed measures, \"amount of adaption\" and repeatability, we could not measure such a relation. Furthermore, the basic results of [PERSON] [2], that vibrotactile feedback assists the precise control of finger forces could not be confirmed in our case. For future studies,  
Figure 4: Estimated repeatabilities per participant \(P_{k}\) and vibration level \(V_{\ell}\) for both performance parameters. No consistent tendency occurred among the pianists, but the vibration levels had a significant influence (marked with *) on repeatability for a majority of the participants. we suggest to include a larger number of participants. This could help to identify groups reacting similarly to key vibrations. Future studies might also include multiple experiments over a certain range of time to exclude influences of physical and mental state on the day of testing. Finally, an analysis on a note-by-note basis could clarify if, for example, the vibrotactile feedback of a long-lasting bass note helps the precise control of the dynamics in subsequent keystrokes. We could not generalize such a relation with the data of the presented experiment. If our results can be confirmed on acoustic instruments, our findings of the perception part of the experiment suggest that piano manufacturers should design the vibrations in the piano keys in balance with the sound of the lower notes of the instrument. Furthermore, it would be interesting to investigate the just-noticeable difference of piano key vibration levels, which might possibly be around 6 dB. Further research in this area could help to answer the question, if the tonal parts of the Steinway and Sons and the Yamaha concert grand pianos (the tonal parts for notes A2, A3, and A4 differ by more than 6 dB [7]) can be differentiated based on their vibrotactile feedback only by the player. Of course in such an experiment the vibrotactile feedback should be rendered on the same instrument, otherwise cues from the auditory or kinematic sensations might dominate the perceived impression. [PERSON] designed, accomplished, and evaluated this study. [PERSON] and [PERSON] contributed as consultants. All discussed the results.