We started our project with intuitive notions on what syntactical differences may arise between protest and non-protest songs. We had a perception that protest music tends to be darker in nature, since the songs typically depict ill-feelings towards something going on in the world. We thought two major phenomena would appear as a result of this: One, we thought the dark nature of protest music would be represented in the lyrics by frequent usage of negation, as the artist depicts all that is wrong and lacking in the current state. Two, we thought protest songs would use very dramatic methods to depict these unsettling situations that the artists are in. We believed that this would be reflected in frequent uses of adjectives to describe the nouns and adverbs to describe the verbs.
Thus, we wanted to compare the frequency of adjectives in noun phrases and the frequency of adverbs in verb phrases between protest lyrics and non-protest lyrics. We used XQuery to pull this data our from our XML files, providing us percentages of verb phrases that include an adverb, noun phrases that include an adjective, verb phrases that are negated, and noun phrases that are negated. We used XSLT to create an SVG that provides a visual representation of the percentages that were pulled in XQuery.
We created an SVG that reported the total percentages of all the phrases that exhibited these characteristics in the protest songs, and we created another SVG that did the same thing for protest songs.
After this, we wanted to create 60 SVGs, one for each song, that reported the percentages of phrases with these traits in that song alone. Because of the large number of desired SVGs, we created a Java program that could automatically parse the XQuery output and, by using XSLT, create the 60 SVGs. This made the process exponentially more efficient.
In order to see the individual SVGs for each song, click on the data page. This page provides a way for users to compare the percentages found in a specific protest song to ones found in a specific non-protest song.
Using our XQuery, we found results for frequency of adjectives in noun phrases and the frequency of adverbs in verb phrases for protest and non-protest songs (as above). We are trying to use those results to come up with a way to determine the following: If we are given a new song where we can calculate the frequencies for the various parts of speech and negation, as we did for our songs, then we can predict whether it should be classified as either a protest or non-protest song.
To come up with this function, we used a Probit Regression Model. Wikipedia defines a Probit Model as,
"A type of regression where the dependent variable can only take two values, for example married or not married. The name is from probability + unit. The purpose of the model is to estimate the probability that an observation with particular characteristics will fall into a specific one of the categories; moreover, if estimated probabilities greater than 1/2 are treated as classifying an observation into a predicted category, the probit model is a type of binary classification model."
In our case, the dependent variable can only take two values: protest or non-protest. We used the statistics package R to do the probit regression and get a classifier function. The idea is that if we pass into this function the values for the frequency of adverbs in verb phrases, for the frequency of adjectives in noun phrases, and for our other calculated statistics, we should get out a probability of our song being a protest song. If the probablitily is very high (near 1.0), then the song is probably a protest son, whereas if it very low (near 0.0), then it is likely that the song is a non-protest song. The problem for classification comes about if the probability ends up being somewhere near the middle (0.5), because then you are basically saying that the classifier function is about as good as a coin-toss for determining whether the song is protest or not.
Unfortunately, our results returned no significant difference in syntax between American protest songs and non-protest songs. Unfortunately, the probit analysis yielded probabilities of about 0.5.
There are perhaps a few different reasons as to why this happened. To start, our analyses were conducted on a very small sample size. If we had more time to expand on this project, we would need to take the time to tag a lot more songs.
Another possible reason why our results showed no difference is that we might have focused on the wrong parts of speech and their relationships in our study. As noted in our methodology, we did not incorporate all components of syntax in our tagging, so we can focus on the ones we were interested in. There is a chance that once we tag all possible phrases and compared different types of relationships, distinctions would appear.
Finally, there is a possibility that there was human error in tagging that involved ambiguity. For instance, we had a feeling that protest songs, where the lyrics tend to be very negative in response to something the artist doesn't like, would incorporate more instances of negation words in their phrases. This may or may not have been the case. However, we restricted our tagging to specific words such as "not" or "aint." If we were to go back into our data and incorporate morphology into the mix, instead of just focusing on the syntax, we could mark up words that were negated but by the use of prefixes or suffixes. One example is the word "impossible," which is defined as "not possible." The word is "possible," but with the prefix "im-" attached to it. If these types of words were included in our data analyses, it might turn out that these lyrics do tend to discuss how things are "not" within the context of their music, rather than what they are, or what they wish they were. This could even expand more into words that, within their definition, are words that mean "not (something else)."