Musical time is split into beats. Beats are accented parts of the music that repeat in regular intervals.
The tempo of a piece a music is a measure of how close the beats are to each other. A piece of music that is 90 beats per minute (BPM) has a faster tempo than a piece that is 60 beats per minute. In order to fit 90 beats into the time of a minute, you have to squeeze the beats closer together.
Today, tempo is often measured in BPM. It is located above the measure indicating the tempo, and is usually marked next to a note indicating the length of the beat as shown by this example:
Often times, you also will find the classical Italian names for tempo.
Here are the BPM estimates of some of the Italian tempo names:
Largo = Very Slow = 40-65 BPM
Andante = Slow = 65-100 BPM
Moderato = Walking Speed = 100-120 BPM
Allegro = Fast = 120-140 BPM
Presto = Very Fast = over 140 BPM
Meter is how we divide up the beats of a musical composition. Usually we don't think of a piece of music as a long string of thousands of beats, but rather split these beats into sections call measures (also called bars). Measures come in different sizes of beats. Pieces of music are usually divided into repeating measures of 2 beats, 3 beats, or 4 beats.
Here is one measure:
Here is one measure composed of 4 beats:
Now I have the beats marked by x's but the concept is clear enough. Count out the beats in an even way 1-2-3-4- and pronounce the "ONE" a little bit louder and repeat: 1-2-3-4-1-2-3-4-.
In written music, however, beats are not signified with x's, but rather with notes. There are several types of notes and any of them can be used to replace the x's as the beats.
Here are the most common notes and their names:
so if we replace the x's with whole notes the measure looks like this:
and if we mark the beats with half notes, the measure will look like this:
Most composers use quarter notes for each beat though:
No matter what note we put in there, the number of beats is the same and is still counted in the same manner: 1-2-3-4-.
The way a composer tells us how many notes are in a measure is with a time signature at the beginning of the musical piece.
So if a musical piece has a measure composed of 4 beats and each beat is marked with a quarter note, then the time signature is 4/4. The bottom 4 meaning "quarter note."
Depending what the bottom number is will tell you what kind of note is used:
Whole Note = 1
Half Note = 2
Quarter Note = 4
Eighth Note= 8
Sixteenth Note = 16
If a piece has a measure of 3 beats and each beat is a sixteenth note, then the piece is in 3/16 time. If a piece has a measure of 3 beats and each beat is a eighth note, then the piece is in 3/8 time. If a piece has a measure of 3 beats and each beat is a quarter note, then the piece is in 3/4 time.
So, in general, we can say that the top number in a time signature is the number of beats per measure. And the bottom number is what kind of note is used to signify a beat.
Here are some of the more common time signatures used in music:
Among these, 4/4 is the most commonly used. In fact, it is sometimes called "common time" and marked with a "c" at the beginning of the music instead of a "4/4".
Relative Note Length
Once we know what note is used to signify the beats in a measure we can figure out how long every other note is played for. For example, if a piece is in 4/4 time, we know that each beat lasts one quarter note. That means that a half note must last for 2 beats, or twice as long as a quarter note.
It also means that an eighth note must last for a half of a beat, since one-eighth is half of one quarter.
Here are the notes and their relative lengths in 4/4 time:
Here is what they look like contained within a measure of 4/4 time:
Notice that the flags on the eighth notes and sixteenth notes are grouped together. Whenever there is more than one eighth or sixteenth note within a beat their flags are connected.
There are also symbols for rests in music. A rest is the absence of sound over a beat.
There are several notations for rests depending on their length. Here are the rests and their values in 4/4 time:
Dotted Notes and Rests
Sometimes we you will see a little dot after a note or rest in sheet music. This means to play the note or rest for 1 and 1/2 times its original value. So a dotted quarter note looks like this:
And it is equal to 1 quarter note plus a half of a quarter note. Thus making the total time equal to 3 eighth notes.
A dotted quarter note rest looks like this and is equal to a quarter note rest plus a half of a quarter note rest:
The dot can be placed after any note or rest in any time signature. It always means to play the note or rest for 1 and a half times its original length.