639 Hz Pure Tone | 10 Hours for Deep Sleep (Black Screen)

639 Hz, ten hours, black screen, no voice. The tone sits at the root of the harmony, so nothing beats against it. The bed underneath is built on 79.875 Hz, which is 639 Hz brought down by three octaves: the same note, lower. The slow movements that make the sound breathe have periods that never line up, so no stretch of the ten hours repeats another. Warm and even. For sleep, or as a steady sound through the night. 639 Hz is one of the nine Solfeggio tones: a tuning tradition, not a medical treatment. Nothing here is health advice. 🎧 Best with headphones or a speaker at low-medium volume. Original sound, digitally generated for this video (not a field recording). No attribution required. Produced for Inner Flows. #solfeggio #639hz #puretone #blackscreen #10hours