Pigeonholing the Style
I think there are two schools of thought on how to define genres in music (or really anything). Most people define a genre as a set of qualities, and pieces of music with those qualities belong to the genre. In this way, a genre can be highly specific—strictly defined, so that all music belonging to the genre must have all the qualities associated with the genre; or very general—either it has very few defining qualities or very few of the defining qualities must be present in a piece for one to consider it part of the genre.
This way of describing music is lazy. Most commonly-used genre names go undefined, and critics who employ them tend to use them however they want, letting genre X stand for whatever bolsters their statement at that moment. Most attempts at defining a genre rely heavily on examples. Most arguments over genre definitions are really just arguments over what performers/pieces belong to the genre. And most statements about music that rely heavily on genres defined in this way, are basically meaningless (if not circular).
This is why I prefer the reverse direction in defining a genre. I define a genre simply by the bands one would describe as making music in that genre. I don't mean here that I use the example bands to grasp the concept of the particular genre. I define genre X as being the set of pieces of music {x}. Any discussion of what all the pieces have in common consists then of valuable statements, rather than simple semantics.
Of course, there's then the question of how to choose which pieces are in the group that is defined as the genre. And here's where I think this way of defining genre is more valuable: it's all historical. The first method of defining genre assumes that you can always describe music by abstract concepts; that the most meaningful statements about a piece of music are made when pulled out of its historical context. This is why it's most useful for the average music listener. He doesn't care about the historical context of music. He wants a lazy descriptor, because generally when he says something pertaining to music he doesn't intend to say something about music.
But music is always contextual, and it's always important to know the history of the musicians involved, when one wants to really know about the music. And with any genre of music, there are always cores of musicians—scenes—and locations where these people are. There is still the full spectrum of strictness. Early-80s-Boston-hardcore—defined by what bands are considered early 80s Boston hardcore—is relatively specific (strict) compared to simply 80s-hardcore.
In some sense, I suppose the real difference between the two ways of defining genre is a change from subjective qualities to objective qualities. Fast, loud, and aggressive are highly subjective. Being from Boston, making music in the early 80s, releasing your records through certain labels and playing concerts with certain other bands are all pretty objective.
The genre definitions are still subjective, because whoever defines the genre chooses which objective qualities it consists of. But this is at least more like a perfect language like mathematics in which, say, an algebra is defined by its commutation relations. You can choose the commutation relations freely, but once they are chosen, the algebra is defined.
I won't say that such music discussions are generally as objective as mathematics, but this way of describing music does eliminate a lot of the filler. I had this topic in my head because I've been reading a lot of definitions of what minimalist music is. In an attempt to keep the posts short, I'll leave that as the topic of the next one.