The dial tone was never meant to be musical. When automatic dialing was introduced in 1919, engineers at the Bell System needed a way to tell callers the equipment was ready.
: Depending on where you are, that "ready" signal sounds different. In the US, it’s a dual-frequency hum; in Europe, it might be a single, higher pitch. Downloading these specific sounds allows users to recreate the "feeling" of a certain place or era. 2. From Utility to Fashion: The Rise of Personalization
: That steady hum is the machine saying, "I am listening". Without it, silence feels like a broken bridge.