Rate effects on timing, key velocity, and finger kinematics in piano performance

Abstract

We examined the effect of rate on finger kinematics in goal-directed actions of pianists. In addition, we evaluated whether movement kinematics can be treated as an indicator of personal identity. Pianists' finger movements were recorded with a motion capture system while they performed melodies from memory at different rates. Pianists' peak finger heights above the keys preceding keystrokes increased as tempo increased, and were attained about one tone before keypress. These rate effects were not simply due to a strategy to increase key velocity (associated with tone intensity) of the corresponding keystroke. Greater finger heights may compensate via greater tactile feedback for a speed-accuracy tradeoff that underlies the tendency toward larger temporal variability at faster tempi. This would allow pianists to maintain high temporal accuracy when playing at fast rates. In addition, finger velocity and accelerations as pianists' fingers approached keys were sufficiently unique to allow pianists' identification with a neural-network classifier. Classification success was higher in pianists with more extensive musical training. Pianists' movement "signatures" may reflect unique goal-directed movement kinematic patterns, leading to individualistic sound.

Figure 1. Results from MIDI analyses.

a) Mean coefficients of variation (CV) of the IOIs (SD/mean IOI) for the five tempo conditions; b) Mean key velocity (tones' intensity) for the five tempo conditions. Error bars are SE of the Mean.

Figure 2. Movement of Finger 1 (thumb) during one pianist's performance of the notated melody at Slow tempo.

Framed notes represent keypresses for Finger 1; vertical lines indicate the time at which the piano keys reached the bottom for each note in the melody. Highlighted regions underscore motion attack regions (dark gray areas) and keypress regions (light gray areas). Key height at rest was approximately 10 mm (+/− 0.5 mm).

Figure 3. Movement amplitude and anticipation time for a portion of the finger height trajectory framed in Figure 2 .

Figure 4. Mean movement amplitude averaged across all fingers for the five tempo conditions.

Errors bars indicate standard errors. Key height at rest was approximately 10 mm (+/− 0.5 mm).

Figure 5. Finger height and phase plane plots of velocity-acceleration trajectory for a pianist's Finger 1 (thumb) movement in the attack and keypress event region (see Figure 2 ).

Black filled circles mark the end of movement, corresponding to full key pressure.

Figure 6. Mean velocity (panel a) and acceleration (panel b) trajectories for Finger 2 (index) in the attack event region for the 4 performers.

Brackets indicate the regions where the difference between performers reached significance (with p<.05, and p<.001 significance values). The x-axis is the normalized time in the attack event region: 1 refers to the keypress of the preceding note (i.e., beginning of the attack region) and 0 to time of occurrence of the actual keypress.

Figure 7. Percent neural network classifications by actual and classified pianist, based on principal components of velocity-acceleration trajectories for all finger movements in the attack event region.

Stars indicate correct classifications or HITS (when the classified pianist corresponded to the actual pianist).

Figure 8. Melodies used in the experiment.