One of the fundamentals of basic music theory and reading sheet music is understanding what a bar in music is, along with all the different bar punctuation symbols.
A bar (or ‘musical measure’) is a segment of music that holds a certain number of beats. The number of beats is determined by the time signature of the song. 4/4 is the most common time signature in Western music.
Types of Bar Lines Explained
There are a few types of bar lines (or ‘measure lines’) to understand:
Single Bar Line
This vertical line indicates the end of a measure or bar. You don’t stop, it’s just so you know it’s the end of that bar.
It’s the most basic music bar line.
Double Bar Lines
Two thin vertical bar lines indicate the end of a section. The double bar line is the same as the single bar line, the only difference is it’s at the end of the section rather than the measure.
Like single bar lines, you don’t stop at these two vertical lines.
End Bar Lines
When you see double vertical lines like this, but the first one thinner than the second line, then it signals the end of the piece or composition.
The musical composition stops at these end bar lines.
Start Repeat Lines
Double bar lines—the first one thicker than the second just like the ‘End Bar Line’ (see above), only this time followed by two dots (like a colon punctuation mark) indicates this is the first bar of a repeated section.
It’s also called a ‘repeat bar line’.
End Repeat Lines
The same as above, only with the double dots before the double line, means it’s the final bar or a repeated section.
It’s sometimes called the ‘right repeat bar line’.
Musical time signatures show you two things. The number at the top indicates the number of beats per bar.
The bottom number tells you the duration of each beat.
In Western music, the most common time signature is ‘4/4’ (also called ‘common time’).
- 4/4 indicates each bar has four beats per bar, and that each beat has the duration of a quarter note.
- 3/4 indicates each bar has 3 beats per bar, and that each beat has the duration of a quarter note.
- 6/8 indicates each bar has 6 beats per bar, and that each beat has a duration of an eighth note.