What does Detective Conan 375 mean after the finale?

Didn't Conan have an absolute sense of music?

When I heard the mountain village police officer call Tottori's grandmother,

I found that the key tone was the same as Belmore's email to the boss of the black organization.

So I asked the mountain village police officer where to call. . Perhaps, the boss of the black organization is there. .

By the way, that key signature 0858 is "Qi つの".

There is also a related collection "Facing the Double Mysteries of Black Organizations and the Full Moon Night"