You may have heard a singer begin a song so quietly that you almost can't hear it, which means they're singing the opening notes dal niente. If it's a recording, you may think you need to turn up the volume.
But don't, because it'll slowly get louder on its own! Dal niente is Italian for "from nothing." The song is meant to start like a sunrise. At dawn, the sky is still mostly dark, and you can't actually see the sun above the horizon yet, but then it gradually brightens until the whole sun is visible in dazzling glory. Music that begins dal niente is like that. The slow build adds to the emotional effect, creating expectation in the listener.