At the very beginning of a piece of music, just after the clef, you will find two numbers, one above the other. This is called a time signature. A time signature gives you two pieces of information:
how many beats per bar there are
what kind of beats we are counting
One of the most common time signatures is 4/4 - it looks like this:
The top number tells you that there are 4 beats in the bar. The bottom number tells us that we are counting crotchets. So 4/4 means there should be four crotchets in each bar. We have already seen lots of examples of music which has four crotchet beats per bar - here is one:
The top number is most often a 2, 3, 4, 6, 9 or 12. However, you could also see 5, 7, 15 or anything else really! Most music written from the Classical to Romantic eras uses a top number from the first group - these are regular time signatures. This means they can be divided up into equal beats (you can divide all those numbers by 2 or 3). The second group are irregular - you can't divide 5, 7 or 15 by anything, so there is no way to divide the bar up into equal beats. Irregular time signatures are most often seen in music written from the 20th century onwards.
The bottom number can only be 2, 4, 8 or 16. Most of the time it is 2, 4 or 8. Very rarely you might see 16 or even 32! The bottom number tells you what kind of beats to count:
2 = minims
4 = crotchets
8 = quavers
Some very common time signatures are 2/4 (two crotchets per bar), 3/4 (three crotchets per bar) and 4/4. All the music you've been reading so far has been in 2/4, 3/4 or 4/4. Here are some more tunes for you to sing. Remember to make a very slight emphasis on the first beat of each bar.
You will also probably have come across 2/2 - two minims per bar. Two minims are mathematically the same as four crotchets, but there is a slight difference in music. In 2/2, it feels like there are only two beats per bar. In 4/4, we feel all four beats. Don't worry if you can't really tell the difference though - most people can't!
The time signature of 4/4 is so common, that it is sometimes referred to as "common time". It's sometimes written as a C, instead of numbers.
So far we have used barlines to divide up the music into equal chunks. The barline we have used is a simple, single, thin line.
Barlines come in different styles however, for different reasons.
At the very end of a piece, we use a double barline. The first line is thin, and the second is thick.
At the end of a section of a piece, we use double barline with two thin lines. This shows you that something new is about to start.
Here, the slow, minim section ends, and a faster quaver section starts.
A double barline with two dots added on the left side tells you to repeat what you just sang.
In the above melody, the repeat barline instructs you to repeat the first two bars, then continue.
Dots added on the right hand side show you where to start repeating from. (They aren't needed if you have to repeat from the very beginning).
In this case, you would repeat bars 3 and 4.
Here are some melodies complete with time signatures and a selection of interesting barlines! Click the play button to hear them - the recordings include the repeats.