At the beginning of every piece of music, there is a time signature that consists of two numbers. One number is placed on top of the other, but keep in mind that the time signature is not a fraction. Each of the two numbers represents a different piece of information.
The upper number (in this case “4”) is an indication of how many counts are contained within the time span of one measure (remember that a measure is the space within two vertical lines that are called bar lines). Because the upper number is four, there will be four counts in every measure.
The top number of a time signature can be anything. A “3” in this position would indicate three counts per measure, a “17” as the top number would mean that there are seventeen counts per measure, and “6.75” would indicate six and three-quarters counts per measure. Yes, although it is very rare, the upper number does not have to be a whole number. It can really be anything — whole, fractional, or whatever.
The lower number of a time signature is a different matter. It can only be one of the following: 1, 2, 4, 8, 16, 32, etc. (powers of two). This is a type of code that stands for a particular note value. A “1” in this position would indicate a whole note, 2 means a half note, 4 means a quarter note, 8 means an eighth note, 16 means a sixteenth note, and 32 means a thirty-second note. Now that we know what the bottom number stands for, what does it mean? The bottom number tells you which note value (quarter, eighth, half, etc.) is equal to one of the counts in the measure.
Here are some examples. In 4/4 meter, there are four counts per measure, and the quarter note is the note value that equals one of the counts. In other words, the time value of a measure is equal to four quarter notes. In 6/8 meter, there will be six counts in every measure, and the value of one of those counts is the eighth note. In other words, each measure will have the time value of six eighth notes. 5/2 meter has the value of five half notes in each bar while a time signature of 3/16 would contain the value of three sixteenth notes in every measure.
If you are getting a little confused about these 3/16 meters, don’t worry. I just wanted you to know the reason why there are four counts in each measure of the exercise, and why we use the counting system of 1, 2, 3, 4 to keep track of them. Remember, that each measure doesn’t have to have only quarter notes. Each measure only has to contain the value of four quarter notes. This lesson will be dealing with other ways to notate the value of a quarter note.
The new figure for this WebRhythm lesson is a group of two eighth notes. A single eighth note is exactly 1/2 the value of a quarter note. In other words, if a quarter note equals one second of time, then a single eighth would equal 1/2 second of time. If a quarter note equaled one inch, then an eighth note would be 1/2 inch. If a quarter note had the value of a dollar bill, then an eighth note would have the value of a 50¢ piece. The reason that I’m making all of these analogies to stress the point that an eighth note is always equal to half the value of a quarter note, no matter what the quarter note’s duration or length happens to be. Using these analogies, you can see that two eighth notes will always equal one quarter note (1/2 + 1/2 = 1).