Volume 10, May 2019
Intonation in the Performance of the Double Bass: The Role of Vision and Tact in Undershoot and Overshoot Patterns

by Fausto Borém and Guilherme Menezes Lage

5. Discussion and Conclusions

The aim of this study was to investigate the double bass as far as the generation of undershoot and overshoot patterns and their relation with the sensorial information required in the performance. The starting point admitted that sensorial guidance (1) improves the accuracy and consistency of musical performance, (2) produces a less pronounced undershoot when compared to the no-guidance condition and (3) creates different undershoot/overshoot patterns in descending and ascending movements.

The results showed that the Integrated Trial (which combines vision, tact and ear) yielded greater precision and a tendency to a lower variability compared to the Free Trial (based on the ear only). These results indicate that the integration of visual and tactile cues increases the quality of intonation in an atonal, spatialized and interrupted sequence of pitches on the double bass, a sequence that comprises major intonation problems found in advanced repertories of the instrument. This fact may contradict the common belief that still prevails in conservative music pedagogy, which favors mainly the ear and do not consider vision and tact as relevant in movement regulation and precision. The findings also corroborate results of previous studies indicating the efficiency of visual and tactile sensorial sources in motor control not only in traditional laboratory aiming tasks (Elliott et al., 2014; Khan & Franks, 2003; Rabin & Gordon, 2004), but also in music performance (Lage et al., 2007). A possible explanation for the improved performance in the Integrated Trial (ear + vision + tact) is that tactile cues work as the first physical reference to the ongoing movement through the anchorage of the left forearm on the instrument, allowing the stabilization of the left shoulder and, consequently, providing an improved and stable movement control. Moreover, visual cues would direct focal vision towards the vicinity of a specific point on the fingerboard (Lage et al., 2007). Therefore, the internal processing seems to improve as far as accuracy and consistency are concerned. Nevertheless, this hypothesis claims for further research.

Regarding the overall analysis, the results showed that an overshoot pattern was produced in the Integrated Trial while an undershoot pattern was typical of the no-guidance trial (Free Trial). The quality of distance calibration in movement planning and online control is a plausible explanation for these results. The richer the structured visual information in a well-structured visual environment is, the better the system calibrates itself (Loftus, Murphy, McKenna, & Mon-Williams, 2004).

The uncertainty produced by the absence of systematic visual and tactile references in the double bass body may have led the participants to explore cognitive strategies responsible for undershoots in the Free Trial and for overshoots in the Integrated Trial. According to Imanaka and Abernethy (1992), undershoot and overshoot patterns can be linked to the specific strategy adopted in a specific task. It is also possible that the strategy may change as a consequence of an ongoing control process. In other words, the participants may have planned the movements to achieve the frequency below the target pitches to prevent the risk of  overshooting and to reduce the probability of activating antagonistic muscles to reverse the movement (Elliott et al., 2014; Elliott et al., 2004; Lyons et al., 2006), what is considered a most embarrassing situation in music performance.

On the other hand, the use of both sensorial cues (vision and tact) may have led participants to achieve a higher degree of sureness and confidence to reach target pitches which, in terms of motor programming and use of feedback, produces an overshoot pattern. Even with this tendency to surpass the target pitch, a higher precision in reaching target pitches was observed in absolute RE measurements. An error in the overshoot pattern below 0.7% can be considered as a non-perceivable deviation, because the capacity of the human ear to distinguish successive and non-simultaneous tones is approximately a tenth of a semitone. Thus, bass players seem more confident to take more risks and make smaller mistakes when resorting to visual and tactile cues besides their ears.

The analysis of movement direction did not detect a well-defined undershoot/overshoot pattern between Free and Integrated Trials. However, the results showed a tendency (1) to achieve a frequency above the target pitch in both directions when sensorial guidance was available and (2) to achieve a frequency below the target pitch in the no-guidance condition. In descending movements (lower to higher registers) performed in the no-guidance condition, this tendency is in accordance with the search for minimum temporal and energetic costs to the system, also observed in other experimental motor behaviour findings (Elliott et al., 2004; Lyons et al., 2006) and in music research literature (Kantorski, 1986; Sogin, 1989). Surprisingly, this system strategy was not found in ascending movements (higher to lower registers) performed under the no-guidance condition. It was observed an overshoot pattern which produced frequencies below the target pitch. This contradicts the expectation of an undershoot pattern in this condition that would occur due to uncertainty of movement control in association with gravitational constraints.

This result allows one to speculate that when uncertainty (absence of systematic visual and tactile references in the instrument body) is present in ascending movements, the system opted for overriding temporal and energetic cost of overshooting (e.g., a longer distance travelled) in favour of achieving a frequency below the target pitch. In a descriptive analysis, the achieved frequency below the target pitch in this condition showed a higher level of directional error (-1,18%) when compared to the same condition in descending movements (-0.61). Possibly, the inherent search for minimization of temporal and energetic costs, which is often seen as beneficial to the system, could in fact need to be dismissed in specialized skills with very high demand of motor control (Oliveira, Elliott, & Goodman, 2005). This is the case for expert music performers in order to avoid the embarrassment of a feared major intonation defect on stage: a noticeable left-hand direction change that can be seen (in movement) and can be heard (in sound) by the audience in the performer's struggle to be in tune.

Further research needs to be carried out to analyse if this behaviour is driven by a perceptual factor in which playing out-of-tune below the target pitches is less uncomfortable than playing out-of-tune above the target pitches in situations performers feel less confident and not so sure about their intonation. Some research findings may support this supposition. Different melodic contours produce different outcomes in auditory processing. In animal models, it was observed that neurons in the auditory cortex of cats reacted differently to the same tone in inverse melodic contour (McKenna et al., 1989). Descending contours, for example, necessarily include shifts from higher frequencies to lower frequencies. The features of the auditory input may modulate motor behaviour, especially if one considers that the integration between auditory and motor systems is very well pronounced in trained musicians (Zatorre, Chen, & Penhune, 2007).

Concluding, the data presented here support the prediction that visual and tactile cues improve music performance accuracy on the double bass as far as intonation goes. Also, regardless of movement direction, the analysis of visual and tactile cues showed the production of undershoot patterns which may be connected to fear and, consequently, muscle contraction. The results regarding movement direction suggest that, in specific conditions of sensorial guidance, temporal and energetic mechanisms may be overruled by some demands of the task. This behaviour, which involves the participant's music embarrassing perception of bad intonation, is a matter still to be investigated. Finally, it is hoped that the results of this research will contribute to more inclusive and more democratic discussions in the international community of bassists, and to the diversity of ways of making music.