# Design and Application of the BiVib Audio-Tactile Piano Sample Library
## 4 Experiments, Applications and Future Work  
BiVib has been originally created to support multisensory experiments in which precise control had to be maintained over the simultaneous auditory and vibrotactile stimuli reaching a performing pianist, particularly when judging the perceived quality of an instrument. In a recent paper, the authors were able to confirm subjective vibrotactile frequency thresholds of active touch [34] by conducting tests with pianists who were asked to detect vibrations at the piano keyboard [12]. A comparison between such thresholds and the spectrum of a lower fortissimo A0 tone is shown in Figure 7. This demonstrates a previously unreported results: during active playing, pianists are able to integrate tactile sensation that would be imperceptible in passive touch conditions [38]. A precise manipulation of the intensity relations between piano sound and vibrations may be used to investigate the existence of cross-modal effects occurring during piano playing. Such effects have been discovered as part of a more general multisensory integration mechanism [39] that under certain conditions can increase the perceived intensity of auditory signals [40], or conversely enhance touch perception [41]. Aiming to understand whether piano keyboard vibrations impact the perceived quality of the instrument and, as a secondary effect, the quality of a performance, the authors have first observed significant differences in the perceived quality of vibrating vs. silently playing Disklavier pianos. This observation marks a point in favor of the former, especially since that pianists involved in the experiment reported to be unaware of the existence of vibratory feedback [12]. In other words, while most pianists preferred the vibrating instrument, they did not consciously realize that their decision was caused by the vibrations produced (or not produced) by the instrument during the performance. Based on this result, a further experiment was designed for the haptic digital piano using  
Figure 7: Magnitude spectrum of the vibration signal at the A0 key, recorded on the upright Disklavier playing at MIDI velocity 111. The dash-dotted curve depicts the reference vibrotactile threshold for passive touch [38], while the two horizontal dashed lines represent the minimum and maximum thresholds recently measured under active touch conditions [34]. Picture adapted from [12]. diverse types of tactile feedback, synthesized by manipulating the BiVib samples. The test aimed at investigating possible consequences of the vibrotactile feedback on the pianist's playing experience (qualitative effect) and on the performance in terms of timing and dynamics accuracy (quantitative effect). Cross-modal effects resulting from varying the tactile feedback of the keyboard were observed, still these preliminary results are far from giving a systematic view about the impact of the different sensory channels on the pianist's playing experience, and especially on the accuracy of execution [20]. Another potential use of BiVib is in the investigation of binaural spatial cues for the acoustic piano. Using the recommendations given in the previous section, single tones of the upright piano can in fact be accurately cleared of the room echoes, and then be reproduced in the position of the ear entrance. The existence of localization cues in piano sounds has not been completely understood yet. Even in pianos where these cues are reported to be audible by listeners, their exact acoustic origin is still an open question [42]. Moreover, visual cues of self-moving keys (a condition possible on Disklavier pianos) producing the corresponding tones, as well as somatosensory cues occurring during active piano playing, may have an influence on localization judgments [30; 32]. One further direction which may take advantage of BiVib deals with research in cognitive neuroscience: recently, pianists and their instrument served as key subjects for understanding diverse aspects of brain and motor development [43; 44].