Metal Networks: Analysis of Decibel Magazine Top 40 2012
I had some free time today so I decided to apply some network analytic techniques to one of my favorite subjects: metal records.
A couple of weeks ago, I attended a lecture on network analysis where the investigators analyzed popular political books on Amazon.com.
Amazon lists not only information on the book but also the titles, in order of purchasing frequency, of other books that customers may have purchased. The researchers here were able to identify left leaning and right leaning books by examining the purchasing habits of Amazon customers.
Decibel “is America’s only monthly extreme music magazine” and has been in publication since 2004. Every year, they publish the titles of the 40 best metal records of the year, according to their review staff.
Here is 2012’s list:
40 Gojira – L’Enfant Sauvage
39 Meshuggah – Koloss
38 Agalloch – Faustian Echoes EP
37 The Shrine – Primitive Blast
36 Incantation – Vanquish In Vengeance
35 Samothrace – Reverence To Stone
34 Devin Townsend Project – Epicloud
33 Panopticon – Kentucky
32 Saint Vitus – LILLIE: F-65
31 Mutilation Rites – Empyrean
30 Author & Punisher – Urus Americanus
29 A Life Once Lost – Ecstatic Trance
28 Asphyx – Deathhammer
27 Farsot – Insects
26 Gaza – No Absolute For Human Suffering
25 Inverloch – Dark/Subside
24 Swans – The Seer
23 Horrendous – The Chills
22 Killing Joke – MMXII
21 Early Graves – Red Horse
20 Liberteer – Better To Die On Your Feet Than Live On Your Knees
19 High On Fire – De Vermis Mysteriis
18 Napalm Death – Utiltarian
17 Torche – Harmonicraft
16 Grave – Endless Procession Of Souls
15 Satan’s Wrath – Galloping Blasphemy
14 Testament – Dark Roots Of Earth
13 Cattle Decapitation – Monolith Of Inhumanity
12 Blut Aus Nord – 777: Cosmosophy
11 Municipal Waste – The Fatal Feast
10 Pig Destroyer – Book Burner
09 Paradise Lost – Tragic Idol
08 Royal Thunder – CVI
07 Enslaved – Riitiir
06 Neurosis – Honor Found In Decay
05 Pallbearer – Sorrow and Extinction
04 Witchcraft – Legend
03 Evoken – Atra Mors
02 Baroness – Yellow & Green
01 Converge – All We Love We Leave Behind
I looked all of these records on Amazon. For each of them, I noted which of the others were in the first 12 titles that were purchased with it, creating a 40 by 40 adjacency matrix where rows (i) and columns (j) represented records. For each entry, a zero was noted where the customer which purchased the i-th record did not purchase the j-th record, and a one where they did.
I found that many of the records on the list were purchased with one another. The most common record purchased in combination with another on the list was Neurosis‘ “Honor Found in Decay.” Fifteen of the other records on this Top 40 were purchased with “Honor Found in Decay.”
In network terms, the Degree of this record would be 15. Pallbearer’s “Sorrow and Extinction” had a degree of 11, Royal Thunder’s “CVI” and Blut Aus Nord’s “777: Cosmosophy” both had a degree of 9.
The network of Decibel’s Top 40 looks like this:
You can see that some records get purchased with other records more than others. The size of the dots represent the degree of the record.
Now, I did some cluster analysis on the data, looking for related groups of records within the network. Using R, I produced the following dendrogram:
There are two major clusters, each with its own subcluster (dendrograms are hierarchical). One includes Converge, Neurosis, Pallbearer Royal Thunder, Evoken and Inverloch with a subcluster including only the first four. These are all bands that might be expected to be purchased with one another. The other big one includes all the rest. Main clusters are designated by color.
I found one containing the three entries for Baroness, Municipal Waste and Napalm Death, very different bands. I’m truly not sure why those three would be in a cluster together (is the cluster is based on lonliness in the network?).
Anyway, I’m done, but glad I got any results at all. I’ll let readers (especially metal fans!) interpret the results.
In the parlance of the recommendation engine industry, those three bands are “less adventurous” recommendations in whatever algorithm is being used, and end up getting purchased by the same people _because_ they are recommended together. This happens because the customers are sampling the genre, rather than because they are die hard fans, and so, as you noted, they end up being “lonely” in _some_ collections, which have only these records in common (for the same reason that Michael Jackson might be recommended when purchasing a Boz Skaggs record). It’s a feedback loop that recommendation engines work very hard to eliminate, but its very difficult to eliminate without a human coming in and saying, hey, those three bands are all very different. Lets put a rule in the algorithm that prevents them from being recommended together. Amazon and iTunes do not have those artificial rules, as far as I can tell.
Of course, that only applies to statistics based on online sales.
You would have been paid well to do this kind of analysis where I used to work. But you would have hated it. It’s only fun if it’s all metal.
Interesting. I hadn’t considered that. Most of the combinations were to be expected, though it was notable that “old” bands (Testament, Swans, St.Vitus) weren’t purchased with the more recent stuff.
People who are buying the recent bands appear to be buying everything that comes out, which wasn’t surprising either.
Someone noted that it wasn’t surprising that Neurosis was the most connected since they have a wide appeal and have been consistently putting put records for a long while.
I could have used the money.