Did you know sound has a shape?
You're probably familiar with a sound wave, where a hertz is one cycle of a wave's oscillation. The more cycles of the sound wave per second, the higher the perceived pitch to the ear because of the spiral of the cochlea. Every musical note corresponds to a specific frequency.
Some musicians have hidden images embedded in their songs that are only revealed through a spectrograph. Nine Inch Nail's album Year Zero features a spectorgaph-made alien hand coming down as the album cover. The song The Warning features this alien hand sound at the end of the song.