Here is the deal with 6/8 time

I had an interesting interaction on a drumming forum recently— it's ongoing actually— there was an extremely long and frustrating conversation involving a whole lot of basic misunderstandings about rhythm and meter.

A user is studying for a college entrance exam, and asked for help answering this example question:

Correct the rhythmic groupings / beamings in the following two bar extract. 

Among the forum users' responses:

There's nothing wrong with the way it's written. [There is.]

It's fine, Portraits in Rhythm has tons of things written that way. [It does not.]

There DEFINITELY aren't enough notes to make a complete measure of 6/8. [There are.] 

Well, in West Side Story the rhythm varied between 3/4 and 6/8 so there's nothing wrong with it. [Exceptions do not invalidate the standard, and anyway most printed versions of Bernstein's America indicate 6/8-3/4]  

How can we know? The instructions don't tell you how to do it. [You're supposed to know.]  

A lot of confused replies about triplets [there are none], about how 6/8 is counted [not in 6], about accents [none], about where the snare drum backbeat goes [???], about note values changing depending on what you call “the beat” [they don't].  

Basically, nobody on the internet understands 6/8 time well enough to pass a college entrance exam, or if they do understand it, they don't know how to explain it clearly and concisely. As always, the most uninformed people are the most vocal in opining about it.


The deal with 6/8 time is: 
It is a compound meter, counted in 2. Compound duple is the descriptive name used in music theory.

Compound means a three note subdivision— a triplet feel, in drummer terms. The opposite of compound is simple, which refers to ordinary meters with a two note subdivision, e.g. 4/4, 3/4, 5/4, 2/2.

Duple means there are two beats per measure. Triple, quadruple, and quintuple meters have three, four, and five beats per measure, respectively.

The beat is the primary felt or conducted pulse in a piece of music. In compound meters like 6/8, that pulse is dotted quarter notes— which are three 8th notes long, which gives us the three-note subdivision.

In light of those facts, this is the correct answer the test writers above were looking for:

Of course there are exceptions— people like to talk their way out of being wrong by finding exceptions. Music in 6/8 played at a slow tempo may be conducted or counted in six. Or it may be played with a strong pull towards 3/4. The definition and notation above is still correct.


Why people are confused
This all gets sorted out quickly the first time you're forced to play The Liberty Bell in middle school band; you hear the music and you see it conducted, and even if the music looks crazy on the page, you figure out how it's supposed to go because the other kids were chicken and made you play snare drum on it*.

But many people are just trying to figure it out by themselves in the practice room, and they don't read in 6/8 often, if they read music at all. They think it is counted in six because a common hack explanation of time signatures confusingly includes the term beat: the top number is the number of beats per measure, the bottom number is what kind of note gets the beat. Obviously that is not the case with compound meters. Unfortunately, a lot of internet sources, including Wikipedia, use that explanation, and it won't go away any time soon.

There is no one-line explanation of time signatures that tells you both what they are, and how to count all of them correctly. What I tell my students is: time signatures tell you how many (top number) of what kind of note (bottom number) fit in one measure. That's it. I then usually explain how to count simple meters, and save explaining compound meters for later. It depends on how much I think the student can process at one time. Understanding it, and being fluent in reading it and playing it, is part of a process more involved than just giving a bumper sticker definition.

* - True story.