Although a measure of music will usually contain four beats, a composer may specify any number of beats for a measure. Waltz time has three beats to a measure, some hymns have six beats per measure. How do you easily determine in the music how many beats there should be in each measure? The answer lies in a reference number given at the beginning of each piece of music. The time signature always appears at the beginning of each piece of music right after the clef, but it can also appear at any point in the music if the time signature changes. The time signature identifies two things: how many beats per measure and which note value gets one beat.
The time signature is always expressed as a fraction. The top number represents the number of beats per measure, and it is the number you count to when playing. The bottom number tells which note gets one beat. Since it is a fraction, a four on the bottom really means ¼ or a quarter note. For now you only need to concern yourself with the top number representing beats per measure. All examples in this book will have four as the bottom number, indicating the quarter note gets one beat. As you progress in your studies, you will learn about other time signatures where other notes will receive one beat.
FIGURE 6-4: Time signatures
Just because the time signature tells you there are four beats to a measure and the quarter note gets the beat, it does not mean that there will be four quarter notes in every measure! Composers may use any combination of notes to fill up a measure as long as their durations add up to the top number in the time signature.