What is a crescendo and a decrescendo?
In music, you can play louder or quieter based on the dynamic or sound markings. In order to change our dynamics or sound level we use a crescendo or a decrescendo. You may want to check out my YouTube video on how to play louder and softer if you are unsure how.
A crescendo has this bird symbol. This symbol means that the music will be quiet at the beginning of the bird beak and when you get to the end of the crescendo you want to be louder. This is used for dramatic effect to really pull the audience in. It's a way to express how exciting or interesting the piece is.
A decrescendo is the exact opposite of a crescendo; it's the same symbol just facing the other direction. Instead of getting louder you want to go from loud to quiet.
A crescendo or decrescendo may last for only a measure or it may last for many measures; it is all about the composer trying to convey to the violinist how much expression he wants you to have. To make a beautiful, expressive piece of music, it's really important to incorporate these two into the style you are playing.