If you haven’t heard of this mystery, start here. The creepiest thing about this — is not the normal transitions — but the three interruptions in the course of twenty years (described here by Wikipedia). The first one occurred on Christmas Eve, 1997:
Ya — UVB-76. 18008. BROMAL: Boris, Roman, Olga, Mikhail, Anna, Larisa. 742, 799, 14.
Here is how it has normally sounded on the shortwave radio station, frequency 4625 kHz. If you still can hear it, please let us know: