Rhythm, though one of the two most basic elements of music (the other being pitch), is also one of the most often misunderstood. Rhythm is frequently presented to students in the form of a hierarchy of note types, with a whole note at the top, two half notes beneath, four quarter notes below them, and so forth. The idea is to teach note values as an introduction to rhythm. But a note does not make a rhythm; it only makes a duration. It takes a sequence of durations to make a rhythm. This is because rhythm must have a beat, and one note cannot signify a beat. One duration could be any number of beats. For example, if I only hear one duration I don’t know if it is two beats at mm = 120, or one beat at mm = 60, or three beats at mm = 180. Without an established beat, there can be no rhythm. If a series of equal durations were to be played, one after the other with no pause in between, the problem would still persist. Indeed, different listeners could conceivably audiate any one of the beats I proposed, and all would be just as correct as the other. They could even audiate different meters, and again all be equally right. From this, we can see that one duration, or a series of identical durations is insufficient to establish beat or meter; therefore, a single duration or a series of identical durations does not qualify as a rhythm.
To qualify as a rhythm, there must be a series of durations that form a repeatable pattern with a clear beginning and a clear end that establishes both beat and meter. The problem with our series of identical durations is that it could begin or end anywhere—there is no way of knowing where it ends until the music comes to a final stop. Even worse, there is no way of establishing a pattern of strong and weak beats that would indicate a meter. Rhythms establish through patterns of differing durations exactly where each beat begins and where it ends, and where each metric beat is located—that is where each strong beat is amid the other weaker beats. Where all of this is clear, there is rhythm, and where there is rhythm, there is a beat hierarchy.
Recall the chart I described earlier—the one with a whole note at the top, divided into two half notes beneath, divided into four quarter notes beneath, and so on. Now we are ready to use this chart in a more effective way than teaching note durations. More effective, because the important issue is not that a whole note, tow half notes or four quarter notes all “add up” to four beats. None of these note types always gets any particular number of beats. The important issue is the relationship between the note types—four quarter notes occupy the same time span as two half notes or one whole note, regardless of how many beats each one gets. According to this, we understand that a piece in common time can be audited at the quarter note level, with quarter notes getting one beat, at the half note level, with half notes getting one beat at half the tempo, at the whole note level with whole notes getting one beat at one-quarter the tempo, or at the eighth note level with eighth notes getting one beat at twice the tempo.
As with melody, we can ask our students if the sound of passing cars on the road, or the sounds of birdsong is a rhythm. We know that one passing car cannot be a rhythm, because it is an isolated duration with no established beat or meter. Several cars passing by separated by long intervals of time pose the same problem, we cannot establish a beat from the time in between each event. Only when cars pass by close enough to each other to establish a beat pattern can we consider those sounds a rhythm. With bird song, it is typically repetitive and in patterns of pitches and durations which afford the listener to establish a beat and a meter; therefore, birdsong is rhythm. After teaching your students the necessity of sounds establishing beat an meter, see if they can fighre out what sounds are or are not rhythm. It is a good problem for them to struggle with. Make sure they can defend their conclusion.