Whistle is a game mechanic in the game Lost in Vivo. Whistling can be done by pressing SPACE on the keyboard, or by pressing Y on an Xbox controller. The player will then whistle.
Whistling is purely optional, as the only true usage it has is pointing you in the right direction during two occasions, and even then it can be ignored if an experienced player knows where to go already. During most of the game, whistling will be disabled, as it has no purpose aside from the two aformentioned parts of the game.
Near the end of the game during a vision of you playing as the dog, your whistle will be replaced by barking. The game does a reverse form of the beginning sequence, as you must listen for the protagonist's whistling to guide you to the end.
During the Sewers, a potential scare can be triggered by whistling before you enter the tunnels where the Eyeless Hobo has left their notes. Instead of your dog barking in response to your whistling, the music will suddenly fade out, and a long, drawn out whistle can be heard from deeper within the tunnels, presumably from the Hobo.