A metronome is a practice tool that produces a steady pulse (or beat) to help musicians play rhythms accurately. The pulses are measured in beats-per-minute (BPM). Most metronomes are capable of playing beats from 35 to 250 BPM. Common uses of the metronome are helping you to maintain an established tempo while practicing, and learning difficult passages.
Time signatures consist of the number of beats in a measure and the value of the beat.
The first step in metronome use is to understand time signatures. Time signatures are found at the beginning of a musical piece, after the clef and the key signature. Time signatures (also called meter signatures) consist of two numbers. The top number indicates the number of beats in a measure, while the bottom number corresponds to the value of the beat. Most often, you will see 2, 3, 4 or 6 beats per measure. Beats are commonly half notes (the bottom number of the meter signature is “2”) or quarter notes (“4”) (the bottom number of the meter signature is “4”).
Here are a few common examples:
4/4: 4 quarter beats per measure (common time)
3/4: 3 quarter beats per measure
2/2: 2 half notes per measure (cut time)
Less easily understood time signatures are those with dotted quarters as the beat (compound time):
6/8: 2 dotted quarters per measure.
9/8: 3 dotted quarters per measure.
NOTE: even though this time signature reads 6 eighth notes per measure, this time signature usually refers to two beats per measure, where each beat is a dotted quarter, consisting of 3 eighth notes.
In western music (whether pop or jazz or classical or other) you either divide the beat into 2 parts (simple time signatures) or 3 (compound time signatures). The beat thus will either be a quarter, half or eighth note (for simple time signatures) or a dotted quarter or dotted half in compound time signatures. Simple time signatures are straightforward to read: 2/4 (two quarters per measure), 2/2 (two half notes per measure), etc.
Compound time signatures tell you the division of the beat because we cannot express dotted values with a number
Compound time signatures (6/8, 9/8, 6/4, etc.) actually tell you the division of the beat because we cannot express dotted values with a number. When the top number is greater than 3 and is divisible by 3 (6, 9, 12), you have to divide that number by 3 to get the actual number of beats per measure. E.g. 6/8: 2 beats per measure (6:3=2), and the beat is valued at a dotted quarter. 6/4: two dotted halves per measure.
If the music is very slow, then the composer may say something like “slow 8ths”. In this case, you would indeed think of the 8th as the beat, but this you will see only at very slow tempi. In general, thinking of the 8th as the beat in compound time (especially at medium and fast tempi) will make the music sound choppy, and again, is simply an erroneous reading of the time signature.
Odd time signatures also exist in music:
5/4: 5 quarters per measure
7/8: 7 eighths per measure
Now that you understand the meter signature, determine the value of the beat and its appropriate tempo for the piece you are learning. For example, your desired tempo might be quarter note=120. (For more information, see the article on tempo markings.) This is quite brisk, and you may not notice it if you sway from it (rush=get faster unintentionally, drag=get slower unintentionally). Having the metronome give you the accurate pulses will help you stay on track.
At other times, most of a piece is easy to play except for a few measures. When faced with a challenging passage, practice the problem area at a slow tempo that allows you to play all the notes without mistakes (at quarter= 78, for example). Then, click the metronome up a few notches and try the passage at the faster tempo. If you can execute the passage 5 times in a row without any mistakes, you can click the metronome up a few notches again. Repeat this process until you reach the target tempo.