At the end of every song you read, you will find a double bar line (or double bar). The purpose of this marking is to tell us that it is the end of the music. It’s like one giant “stop sign” commanding you to come to a screeching halt when you see it.
What It Looks Like
The inner line is thin while the outer line is very thick. Every time you see this marking, the thick line will always be on the outside. If not, then it is something else we’ll talk about more in just a moment.
Just like bar lines, they will always pass through the entire staff vertically, including the grand staff.
This may be because we do have another “special” type of double bar line that is used to create larger sections in the music. These sections are made up of several measures in music and indicate a change or something different in the music. In this case, the outer line of the symbol is not darkened or thick. Both lines look exactly the same.
So, a double bar line or a final bar line does nothing more than tell us that it is the end of a song. It acts like a “stop sign” signaling to us that we are approaching the end of the piece. Even though you may find this symbol called by other names, it is still most commonly referred to as a double bar line by most musicians and professionals.
Also, be sure to note that we have two different kinds of double bar lines, one that ends a section and the more common type that means “the end”. If you are new to reading music, just focus on the ending double bar line or “final bar line” right now. The other double bar is much less important.