Time Signatures

What are Time Signatures?

Meter is indicated in music notation with time signatures, which consist of two numbers: a top number, and a bottom number. These numbers establish the relationship between the beat and the written rhythms.

The bottom number of a time signature stands for a rhythmic value - 2 means half note, 4 means quarter note, 8 means eighth note, and so on (see Rhythm for more details). The top number indicates how many of this designated note will constitute a measure. That is, a 2/4 measure contains two quarter notes, a 2/2 measure contains two half notes, and so on.

So, what is the relationship between these groupings and the beat? To answer this, first we must discuss simple meter and compound meter.

Simple Meter

In simple meter, the duration of note indicated by the lower number will almost always corresponds with the beat. For example, in 3/4 time there are three quarter notes in a measure, and the conductor (or metronome) will beat each of those three quarters. To put it another way, if the orchestra were to play only quarter notes, they would play one quarter note for each click on the metronome or beat of the conductor's baton.

As a second example, in 2/2 time, the conductor's beat would correspond with the half note instead, and there would be only two clicks per measure. In this case, if the orchestra were to play only quarter notes, they would play two for each beat. Thus, if the conductor were to beat exactly the same tempo (beats per minute) as he had for 4/4 time, the piece would essentially go twice as fast.