One of the most baffling concepts in music is the idea that some meters are compound while others are simple. Something that is compound is made up of two or more parts each of which is itself a complete entity. In language, a word like lifetime is a compound word because it is a single word with a meaning but made up of two words, life and time, that each have a separate meaning.There are also compound sentences, which are sentences made up of two or more clauses, each of which has a distinct meaning, connected by a conjunction such as and or but. For example, the sentence “apple trees bear fruit, but maple trees do not bear fruit” is a compound sentence.

In music, six-eight meter is considered compound, whereas two-four meter is considered simple or not compound. If this is so, then we would expect to find two or more distinct patterns of strong and week beats joined together in six-eight but not in two-four. The problem is, this simply isn’t the case. Either meter could be considered simple or compound, depending on how one defines the elements that are or are not present. In six-eight meter, there are both eighth note beats and dotted half note beats occurring simultaneously; two dotted quarter note beats per measure, and three eighth note beats per dotted quarter. With these two elements joined together, this could qualify six-eight time as being compound. But in two-four meter, there are eighth note beats and quarter note beats occurring simultaneously; two quarter note beats per measure, and two eighth note beats per quarter note–so why isn’t that considered compound? In music, rhythmic and grouping structure can be perceived at any note value level. There are eighth note, quarter note, half note, and even whole note beats perceived by both performers and listeners, and theses beats are always present simultaneously, even in so-called “simple” meters.

The standard explanation for compound meter really has nothing at all to do with the concept of compound. That explanation is that when a beat is divided into three equal parts, the meter is compound, and when it is divided into two equal parts, then it is simple. While this agrees with the designations of six-eight as compound and two-four as simple, there is nothing there that is truly compound. With this definition, there are not two or more elements joined together. Whatever six-eight time is, three divisions of each beat cannot qualify it as compound. It would be more palatable if the word complex were used instead of compound. Researchers, including Temperley and Lerdahl have found that people prefer duple meter to triple meter, so it may be that in some way a beat divided into three equal parts is more complex to our human minds, but that does not make it compound.

If all of this is so, then why is six-eight meter called compound? What are the two elements joined together to warrant that designation? Many students and even some teachers miss this because they are devoted to the idea that the bottom number in a meter signature indicates the kind of beat that gets one beat; however this is not always true, and is the key to understanding what compound meter really is. In all of the compound meters, the bottom number in the meter signature is never the number of beats in each measure. The bottom number indicates one type of note, but performers and listeners alike treat another kind of note as the pulse or ictus as it is often called. In six-eight time, the bottom number indicates an eighth note, but the kind of note getting one note is a dotted quarter note. Here we finally have our two elements: the note value shown in the bottom number of the meter signature, and the note value that is actually the beat. In meters that are not compound, the bottom number in the meter signature is always the same as the kind of note that gets one beat. Because the bottom number indication and the ictus are the same, there are not two elements joined together, but one shared by both the meter signature and the ictus.

With this problem solved, we now move on to the other area of confusion concerning meter designations. What determines if a meter is duple or triple? Traditionally, the number of beats in a measure was the determining factor. Two beats per measure are considered duple meter, and three beats per measure are considered triple. Some add to this quadruple meter, which is four beats per measure, while others hold that four beats per measure is to the listener indistinguishable from two beats per measure, and so is also considered duple. Then there are others, most notably Gordon, who have argued that the number of beats in each measure has nothing to do with determining a meter to be duple or triple, but rather it is the number of divisions within each beat. By this reasoning, six-eight time is not compound duple, but usual triple, while two-four meter remains duple, though because the quarter note beats are divided into two eighth notes, not because there are two beats in each measure.

In the end, it all comes down to grouping. Meter, by definition, is a pattern of strong and weak beats. The key to perceiving any meter is into what groups do our minds organize the music we have just heard? Do we hear patterns in which a strong beat occurs every three beats or every four beats? If number of beats per measure is the deciding factor, then we must be hearing only the first beat of each measure as a strong beat, and all other beats within the measure as weak. Because this is not always the case, it must be admitted that number of beats per measure is not always an indicator of meter. Although Richard Strauss’ Til Eulenspiegel’s Merry Pranks is written in six-eight time, which should be compound duple meter, anyone is hard pressed hear those opening bars in groups of two beats while overlooking the rapidly moving groups of threes played by the horn. Nor do most hear the Andante Cantabile in the Fifth Symphony of Tchaikovsky and perceive duple or quadruple meter. That glorious music can only be heard in metrical groups of three.

We now understand the meaning of the terms compound and simple in regard to musical meter, and we have also seen that these designations can be misleading or inaccurate, particularly in cases where the meter is designated as compound. Relying on the number of beat divisions instead of the number of beats in a measure is more accurate. There are times when the two will agree, and those times will invariably be when the perceived ictus is found to equal one measure, as with a waltz or very quick march. But this is not always the case, and so cannot be a reliable method. Because of this, the terms compound and simple do not add much to most people’s understanding of music they hear, and more often unnecessarily confuses them. Because they are often used terms, it is necessary to understand them, but also to understand their limitations. Always let your performing and listening be guided by what you audiate, and remember that the notation is the composer’s best effort to pass on to others what he or she audiated when creating the music. Theory is inferred from practice and not the other way around.