Dynamics, articulation and form
Repeat sign
A repeat sign is a double bar line with two dots. When you reach it, go back and play the passage again; the second time, play on past the sign.
The closing sign :| (dots on the left) marks where the repeated passage ends. If the repeat does not go back to the very beginning, an opening sign |: (dots on the right) marks where it starts: at the closing sign, jump back to the opening one. With no opening sign, go back to the start of the piece.
A repeated passage can end differently the second time. A bracket marked 1 over the measures is the first ending, a bracket marked 2 the second ending (also called first and second volta). The first time through, play the first ending and go back; the second time, skip the first ending and jump straight to the second.
One more road sign is D.C. al Fine (da capo al fine, from the beginning to the end): go back to the start and play until the word Fine. Repeats save space and also show the form of a piece: what repeats is one section.
What it sounds like
A repeat is heard as a return: the same phrase comes again and the ear recognises it. That is how a piece takes shape.
Where it is taught: the studio’s interactive textbook, chapter 18, “Tempo, repeats and form”.