How does the Black/White Flute work and how long does the effect last?

Question

Does it work like a repel/reverse repel respectively? How long does the effect last? How is the mechanic to determine whether Mons' are repelled/lured, respectively, after the use? If Black Flute works like an unlimited repel, then It might be useful for my next radar chain adventures.

Answer 1

When used in the field, reduces wild Pokémon encounter rate by 50%. This effect will last until a map transition takes place.

Black Flute

When used in the field, increases wild Pokémon encounter rate by 50%. This effect will last until a map transition takes place.

White Flute

They don't work like repels. They just mess with the rng to either increase or decrease your rate of encountering a wild Pokemon. Black flute doesn't work like unlimited repel. It just makes it less likely for wild mons to appear. Also, since all of this is rng, nothing is too guaranteed