Making music together demands maximum performance from our brain: We not only have to concentrate on which notes have to be played when and how, but also pay attention to our fellow musicians and coordinate with them. Using an MRI-compatible piano specially constructed for the research, scientists have now observed how pianists’ brains work while playing a duet with a partner. Accordingly, the musicians play the voice of their partner in their head. In the case of rhythmic discrepancies, on the other hand, they concentrate more on themselves.
What happens in the brain while we make music? This question is usually difficult for scientists to explore because MRI scans, which provide insights into the brain, not only require the head to be perfectly still, they also take place in a narrow tube with a strong magnetic field. However, in cooperation with a piano manufacturer, researchers at the Max Planck Institute for Human Cognitive and Brain Sciences in Leipzig have succeeded in developing a piano that musicians can play in the MRT. With only 27 keys, the instrument is small enough to take with you into the tube. To avoid problems with the magnetic field, the keystrokes are transmitted via optical fiber. In previous studies, the researchers used this to examine what happens in the brain when playing solo.
Pianists in the MRI
A team led by MPI researcher Natalie Kohler has now observed the brains of pianists making music together. To do this, the researchers first had 40 people who have been playing the piano professionally for many years practice eight short pieces of music each – sometimes both the melody and the bass voice, sometimes just the melody. While the first part of the piece was always to be practiced at the same tempo, the researchers instructed the subjects to rehearse the second part at both a fast and a slow tempo.
For the experiment, two people played music together, with one person lying in the MRT playing the melody with his right hand, the other person playing the bass part with his left hand on a normal electric piano. Meanwhile, the researchers observed the person’s brain activity in the MRI scanner. “If the pianists knew the bass voice, the brain regions responsible for the motor function of playing this voice were active – even if it was played by the partner outside,” reports Kohler. “At the same time, however, regions responsible for hearing were also activated. This means that the pianists not only played the bass part in their head as an accompaniment, but even imagined its sound, which of course was not always identical to the playing of the partner.”
Cerebellum detects asynchrony
Before the beginning of each piece, a brief indication showed whether the second part of the piece should be played fast or slow. The trick: While the test persons believed they had received the same instructions as their partner, the researchers gave incongruent instructions in some experiments, so that one musician was prepared to continue the piece slowly, the other quickly. It is known from previous studies that this expectation already has an effect on playing the first part at a fixed tempo. So that the subjects did not notice that their partner had received a different instruction, the researchers muted both pianos in the second part of the piece and only analyzed the interactions in the first part.
As expected, a tiny rhythmic asynchrony crept in with incongruent instructions – which the brain apparently registered immediately: “If the partner pressed the keys at a different tempo than expected, the cerebellum, which is a good detector of temporal discrepancies, was activated. This is remarkable since we are only talking about a few milliseconds difference here. We are therefore in the absolute high-performance sector,” says co-author Daniela Collector from the Max Planck Institute for Empirical Aesthetics in Frankfurt am Main.
Division of tasks between the musicians’ brains
While other studies have repeatedly shown that the musicians adapt quickly to each other in such cases, the researchers found a different effect in the people in the MRI: “The more the cerebellum was activated by temporal asynchrony, the less the pianists adapted their playing that of the partner,” they report. Instead, the brain activity suggested that the person on the MRI was more focused on their own gaming.
On the other hand, the pianist on the electric piano who was not in the extraordinary MRI situation actually adapted to his partner. The researchers suspect that this effect is due to an intuitive understanding between the musicians. This allows the one playing in more difficult conditions to focus more on themselves while the other takes on the cognitively difficult task of synchronization. The study thus provides initial insights into how the brain links cognitive and sensory factors when making music together, thus making it possible to adapt one’s own playing to the situation.
Source: Natalie Kohler (Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig) et al., Cerebral Cortex, doi: 10.1093/cercor/bhac243