As those of you have been following this blog probably know, I’m quite interested in visualizing social networks (for example, Last.fm). One interesting application of this is the visualization of historical movements. I initially thought of looking at the relationship between artists as a function of when they created their works and who they collaborated with, but quickly realized that such data would be nearly impossible (at least for me) to collect or compile. And so, I turned to a related area, classical music.

While there are certainly plenty of classical composers, the breadth is smaller, and perhaps the relationships have already been cataloged. A quick google search proved me right. Charles H. Smith, Professor of Library Public Services at Western Kentucky University complied such a database in 1993 called The Classical Music Navigator! Unfortunately, since the site was created back in Web 1.0 times, the data were not accessible via an API or even via a conventional web crawler (due to formatting inconsistencies caused by static web pages). As such, I contacted Prof. Smith and he was kind enough to send me the underlying data (though still in a format that required a few hours of parsing).

Anyway, after playing around for a while, I was able to map the relationships between 444 classical composers starting from Hildegard in 1098 through the present day. Using Tulip to do the heavy lifting, I came up with the following:

What we see here is a 3D representation of the 444 composers. Each white sphere is a composer and each line represents a connection. For this visualization, a connection represents a point of influence. In other words, every time The Classical Music Navigator indicated that composer A was influenced by composer B, a link was created. The size of the spheres represents the number of direct influences that a composer has had. This resulted in 2,618 direct relationships. The bluer the line the younger the composer (bottom) and the redder the line, the older the composer (top).

Because I don’t know how to export Tulip data into any kind of 3D software (I’m not sure if it’s even possible), I decided to make a video tour which not only showed the 3D’ness of the visualization, but also highlighted some neat aspects of it.

If you’ve made it this far, than you might be interested in some more information about the data. Let’s start with a histogram of the number of direct relationships per composer.

Nothing surprising here. A strong positive skew suggesting that most composers had little influence.

Interestingly, when one only uses the number of direct relationships as a metric for influence, one misses out on all the indirect influence a composer has had. What I mean by this is that composer A may have influenced composer B who in tern influenced composers C, D, and E. Looking only at direct relationships, we would say that composer A was not influential as he had only 1 connection. However, if we look at the indirect effect (the effect A had on all of B’s influences) we find that A actually had 4 (B,C,D, and E) connections. Following this type of logic, we come up with a different interpretation of the results. Here is a histogram of the number of indirect relationships each composer has had:

And now a scatter plot of both direct (x-axis) and indirect (y-axis)

What we see from the scatter plot is that there are quite a few composers who had very few direct relationships (on the left) but very many indirect relationships (at the top). Of course, we would expect that older composers would have strong indirect influences just by virtue of being around earlier. We can examine this hypothesis by looking at a scatter plot of the # of indirect relationships by the birth year of the composer.

Here we see that while there is a clear negative relationship suggesting that, yes, indirect influence is a function of birth year, we also see that the relationship is not quite perfect. Several composers have an indirect influence of about 200 spanning the time range and some have no influence at all.

If I recreate the visualization using the # of indirect influences to determine the size of each node, you get a slightly different picture.

Here we see that the composers at the top generally have much more influence than the composers at the bottom, as we’d expect. However, we also see that many composers throughout the visualization have had a large influence on classical music.

If you find this interesting, I suggest you take a deeper look at the data by either going to the Classical Music Navigator and playing around or by downloading Tulip and playing with the model yourself.

I’m making the Tulip data freely available here.

This entry was posted on Thursday, March 6th, 2008 at 3:33 pm and is filed under Visualization. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.