Approximately every eleven weeks, somewhere in the GLMZ transit corridor, a group of between forty and three hundred people simultaneously stop walking, tilt their heads back, and produce a sustained harmonic tone for exactly ninety seconds before dispersing without acknowledgment or explanation. Participants later report no memory of the event but describe a sense of profound resonance — a feeling that something was 'tuning' them. Acoustic engineers who have recorded the phenomenon note the chord produced is not achievable by unaugmented human vocal cords and contains subsonic elements that affect nearby BCI users. The phenomenon has been documented in transit hubs, pedestrian bridges, and twice inside Vantabloc Corporation's Tier 4 atrium, which caused significant corporate alarm.