Synaesthesia is when sounds trigger certain feelings or emotions in the audience, this is used in many different ways, but it is most popularly used in the film industry, as to help transfer the feelings that the producer wants the audience to feel.

A great example is this video of Dark suspenseful music, we listened to the video without watching the video and write down what we thought the music made us feel.

These are what we thought of when we listened to the video, and as you can see it clearly conveyed very eeire and creepy sounds to the audience.