“I can keep perfect time. Some call me the Human Metronome. You notice how I’m always on time? I’m never late for things.” — George Michael Bluth
Time signatures are something that I know how to use without really knowing how I’m using them, why I’m using them, or what they really mean. As I’m learning, their purpose is to indicate to a musician how to count each beat so that the music is played as it was written to be played and so that when multiple musicians play together they are on the same page, so to speak.
Time signatures are written like a fraction. The top number tells the musician how many beats to count in a measure. This number usually is between 2 and 12, but could be any number, really. The bottom number corresponds to what kind of note will be counted. A 2 in this spot indicates half notes will be counted, a 4 indicates quarter notes, an 8 indicates eighth notes, and so on. Theoretically any number can go in the denominator, but the most common are 4, 8, and 16.
To illustrate: In a 4/4 time signature all notes and rests must equal four quarter notes in each measure. The player knows there are four because the top number is four, and knows that they are quarter notes because the bottom number is four. This does not mean that each bar will contain solely four quarter notes (if that were the case music would be much easier to play and much less exciting to listen to). It means that any eighth notes or sixteenth notes or rests or half notes must all combine together to equal four quarter notes in each measure and that each beat is a quarter note in length.
Below is a short example of a ¾ time signature. Each beat in the song is the length of a quarter note and there are three beats in a measure. It is from Franz Lehár’s “The Merry Widow” (or, as they say in German, “Die lustige Witwe”).