The Coaching Whistle is a Character-specific craftable Item exclusive to Wolfgang in Don't Starve Together. Once Wolfgang has unlocked the Coach Wolfgang Skill in his Skill Tree, the Whistle can be crafted by Wolfgang in his Survivor Items Filter, requiring 1 Flint and 1 Rope. The Whistle only has an effect when used by Wolfgang in his Normal form. While active, it will motivate nearby players and followers (including other players' followers) every 10-40 seconds within six Pitchfork tiles. Players will receive a sanity gain of 5 and followers will receive a 9.5 second double damage buff.
Wolfgang will continue coaching even after dropping the whistle; however, reverting to Wimpy or Mighty form will cancel the coaching. This means it is difficult to fight alongside your followers, as attacking will increase your mightiness until the effect is eventually cancelled when Wolfgang becomes Mighty. Without any manipulation, followers' double damage buff will be active only roughly one third of the time, due to the average time it takes for Wolfgang to trigger his motivation while coaching.
Here is a list of creatures that can be affected by the Whistle:
If Wolfgang stops coaching a few seconds after the motivation triggers and immediately starts coaching again, he will only have a 7 second cooldown to motivate again. Effectively, Wolfgang's coaching can have close to 100% uptime if managed correctly. However, if done too early, he will have the random 10-40 second cooldown to motivate after starting to coach.