Bimanual Control and Classical Guitar Performance

Classical guitar performance is a complex, bimanual task.

In fact, it is a uniquely difficult bimanual coordination task due to a few factors.

  1. The movements are extremely fine. One could argue that the difference of a millimeter here or there is important for beautiful tone, not to mention the right notes.
  2.  Individual finger movements must be perfectly timed between both hands.
  3. In certain pieces you might be playing hundreds of notes per minute.
  4. Each hand is performing a different type of task, with different vectors and forces: either fretting or plucking.
  5. The arms are not held in a static position, which can be detrimental to the stability of bimanual coordination (Carson, 2000).
  6. The movement is anti-phase. Essentially the body prefers movements that are in-phase or mirrored. That is why it’s so difficult to tap your head and move your other hand in a circle around your stomach. The body naturally reverts to in-phase movements so you end up tapping both hands in a circle.
  7. Guitarist often pluck (flex) their fingers on off-beats, which like anti-phase movements, the body doesn’t particularly like to do.

So how is it done? Theories around bimanual control essentially ask the question:

How can bimanual movement be so fluid, when there are so many degrees of freedom as well as different brain areas and networks involved?

The short answer is constraints.

” .. the more the constraints act in coalition, the more stable and accurate the coordination pattern will be. Conversely, when constraints are in conflict with each other, performance will deteriorate.” (Swinnen, 2004, p. 19).

The ‘degrees of freedom problem‘ shows that there are many different ways for the body to perform a single action.

For example, there are numerous ways in which finger of the right hand can pluck string 1. The finger and wrist joints can all angle in different ways (Ida Presti’s right-hand technique comes to mind). Shoulder and elbow can be aligned in different ways. Guitar size and footstool height will alter body positioning. Free-stroke vs. rest-stroke. The list goes on.

So there are many decisions to make in order to pluck a single note, and this is part of the reason why guitar performance is difficult to learn. There are so many, many choices to make regarding finger, hand, arm and body positioning. There is also no dedicated ‘area’ for bimanual control in the brain. Instead, bimanual coordination is seen to arise from a network of corticospinal areas and multiple cognitive levels, from perceptual to neuromuscular (Swinnen, 2004). For example, some research indicates that different networks are used for bimanual responses that are internally (ie. memorized music) vs. externally generated (ie. sight-reading notation) (Debaere, 2003).

While bimanual coordination is seen to involve multiple brain networks and not distinct loci, adaptations for bimanual coordination in musicians can be seen in particular in an increase of corpus callosum (the fibrous white matter that connects the two hemispheres) (Schlaug et al. 1995; Lee et al. 2003) which is seen as facilitating communication between the different hemispheres of the primary motor cortex (M1), SMA and premotor cortex (Watson, 2006). 

So how does the brain control complex guitar movements with so many different decisions to make simultaneously?

Part of the answer is, it doesn’t. Even in improvised music the motor tasks are largely automated through practice (Pressing, 1988; Norgaard, 2014). What you do in the practice room will be there on stage, there is no other way around it. To have fluid performances, it is essential for your brain to limit how many decisions must be made in the moment – so it practices one way to do things and repeats as needed. If you’ve ever made one mistake, only to find yourself repeating the same mistake over and over again, that is what is happening.

(Note: a good fix for this is to alternate between slowly repeating the mistake on purpose and playing the correct sequence.)

Practice is a means of applying cognitive constraints, which stabilizes bimanual coordination.

The precision and automaticity in musical movement patterns can be seen in (Baader, 2005) a study of violinist’s bowing and fingering which showed that the left-hand movements were extremely consistent from trial to trial. This is also indicated in guitar studies such as (Wright, 2012) which found that experts required less preparation and had smaller motor potentials (measured by EEG) than beginners prior to movement onset. So in essence, music practice automates complex, anti-phase bimanual movements, in addition to restructuring the brain over time to accommodate ongoing task complexity. Through practice, extremely complex movements are made automatic and the capabilities of the musician fundamentally altered through the process of neuroplasticity.

There is a cost to this as well, though. You might note that it is occasionally difficult to begin a memorized piece anywhere but a few set points. This is because your brain has bound sequences of movements into a whole, beginning to end. Some of this ‘binding’ is conceptual. If you see images while you play a certain section; or use graphic hand shapes to remember certain passages, this is perceptual control of movement. Large complex movement sequences can be clustered together using symbols or graphic representation (Wenderoth, 2009).

And if that sounds unbelievable, well you actually do it all the time.

 

rcm_aguadoandantino

 

These graphics indicate bimanual movement sequences. And most of the sequences (for experienced players) will be automatic, triggered by the visual stimuli.

So it is not hard to imagine how guitarists may perform long pieces of complex music from memory. The movements are automated through practice, and the brain uses symbolization or perceptual control to ‘bind’ sets of sequences together as a whole.

 

References:

Carson, R.G. et al. (2000) Neuromuscular-skeletal constraints upon the dynamics of unimanual and bimanual coordination. Exp. Brain Res. 131, 196–214

Baader, A. P., Kazennikov, O., & Wiesendanger, M. (2005). Coordination of bowing and fingering in violin playing. Cognitive brain research, 23(2), 436-443.

Debaere, Wenderoth, Sunaert, Van Hecke, & Swinnen. (2003). Internal vs external generation of movements: Differential neural pathways involved in bimanual coordination performed in the presence or absence of augmented visual feedback. Neuroimage, 19(3), 764-776.

Lee, D. J., Chen, Y., & Schlaug, G. (2003). Corpus callosum: musician and gender effects. Neuroreport, 14(2), 205-209. 

Norgaard, M. (2014). How Jazz Musicians Improvise. Music Perception: An Interdisciplinary Journal, 31(3), 271-287.

Pressing, J. (1988). Improvisation: methods and models. John A. Sloboda (Hg.): Generative processes in music, Oxford, 129-178.

Schlaug, G., Jäncke, L., Huang, Y., Staiger, J. F., & Steinmetz, H. (1995). Increased corpus callosum size in musicians. Neuropsychologia, 33(8), 1047-1055. 

Steele, C. J., Bailey, J. A., Zatorre, R. J., & Penhune, V. B. (2013). Early musical training and white-matter plasticity in the corpus callosum: evidence for a sensitive period. Journal of Neuroscience, 33(3), 1282-1290.

Swinnen, S. P., & Wenderoth, N. (2004). Two hands, one brain: cognitive neuroscience of bimanual skill. Trends in cognitive sciences, 8(1), 18-25.

Watson, A. H. (2006). What can studying musicians tell us about motor control of the hand?. Journal of anatomy, 208(4), 527-542.

Wenderoth, N., Van Dooren, M., Vandebroek, A., De Vos, J., Vangheluwe, S., Stinear, C. M., … & Swinnen, S. P. (2009). Conceptual binding: integrated visual cues reduce processing costs in bimanual movements. Journal of neurophysiology, 102(1), 302-311.

Wright, D. J., Holmes, P. S., Di Russo, F., Loporto, M., & Smith, D. (2012). Differences in cortical activity related to motor planning between experienced guitarists and non-musicians during guitar playing. Human movement science, 31(3), 567-577. 

 

 

 

 

 

 

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