Bach and the Brain

Johann Sebastian Bach is the world's most popular composer.

According to Spotify, almost 7 million people stream Bach each month. His listener count is higher than Beethoven or even Mozart. His Prelude to Cello Suite No 1 in G Major has been steamed hundreds of millions of times. 

What makes Bach so popular? Critics will suggest it's his unorthodox harmonies, intricate counter point and compositions that are symmetrical. 

Researchers have begun representing Bach's music as a network. In the network, each node stands for one single musical note. Each edge is the transition from one note to another. An interesting picture is formed. 

A large group has been studying Bach's music in network form and released a paper in Physical Review Research. The ground included Dani S. Bassett, J. Peter Skirkanicha (Professor in Bioengineering and in Electrical and Systems Engineering) with the Perelman School of Medicine and with S. Kulkarni, doctoral student. 

The group applied network theory to Bach's entire works. The paper shows the potential for analyzing music using networks. Such assaying could being beneficial to music therapists, composers, musicians and even music producers.  Music producers would get unequaled measurable insight into the structure of difficult musical frameworks. 

"This paper provides a starting point for how one boils down these complexities in music and starts with a simple representation to dig into how these pieces are structured," reports lead author, Kulkarni. "We applied this framework to a dozen types of Bach's compositions and were able to observe quantitive differences in how they were structured."

In 2020, an assistant professor in Physics at Yale named Christopher Lynn was a student in Bassett's Complex Systems Lab. He developed an analysis of information in complex networks that accounts for how people understand information. Lynn, who also worked on the new paper, applied the network framework to five pieces of classical music, including one Bach piece.

"It was really interesting just to see how our model helped us to understand the structure of those pieces. From there we realized if we wanted to say something meaningful about music more generally, you can't use a handful of pieces. You need to use a larger data set,' reports Lynn.

Bach wrote more than 1,100 pieces. The team has rewritten the works as networks of notes and the transitions between them. "We hear one note and the next and the next and the next. So a song is just a sequence of pieces of information," says Bassett.

Two crucial measurements researchers found were entropy and clustering. Networks that had higher entropy contain more information. This is where any given node can connect to many other nodes. Lower entropy contains less information. Clustering is when the network's content overthrows expectations. Low clustering means that the network strays from expectations.

"Language networks have a very high entropy. So they are very complex-they're packing in a lot of information, but have a low divergence from our expectations. And music is sort of the opposite. It has less complexity in general, but it frequently diverges from our expectations." reports Bassett.

When researchers in the future use the networks, they will be able to explore the relationships between musical compositions and the listener's brain. "If we understand how one person responds to different levels of complexity in a piece. . .that may help us guide the kinds of music that we recommend for a particular therapy," says Bassett. 

Spotify, producers and composers alike will all benefit from how different musical compositions affect the brain. 

The researchers discovered that Bach's toccatas had a high level of entropy as compared to his chorales. Chorales are simple and repetitive, sung in church and meant to spur adoration and relaxation. Tocattas are complex and were written for entertainment. 

Kulkarnin will be studying other genres soon, even studying jazz music.  "I'm very curious what sorts of differences we'll see across these different cultural traditions," says Kulkarni.

An interesting study on the world's most popular composer!