Create a sketch that analyzes sound and translates it into something visual. Use live or recorded audio. Use color, video, images, pixels or whatever you fancy to represent the sound.
Combining Shiffman’s Firework with p5.sound, I made sound-triggered fireworks. I used FFT to analyze the sound and generate a firework when one specific frequency’s amplitude changes in a huge amount. The position x of each fireworks is representing its frequency.