Mysteries can be melodic

Accidentally I stumbled upon this one. Log details: 8147 kHz AM 2214z-2215z. Known as X06, it is believed to be a Russian SELCAL system nicknamed "Mazielka".

There are hundreds of different tone combinations that can be heard. I know at least one dedicated fan of them, but anyone agrees that the tones are melodic and distinguish from all the other strange-sounding signals found in HF.