Whistling/Humming

Almost anyone can whistle or hum. Those who take this proficiency are exceptional whistlers and hummers. They can produce tunes as captivating as most songs. A person with this proficiency is a true master whistler and hummer.

It is so easy to learn a new tune to whistle or hum that characters with this proficiency can learn numerous tunes. In fact, if a proficiency check is made, a whistler or hummer knows any particular tune in question. In addition, a character with both this proficiency and the animal lore proficiency can mimic any bird call he has heard.

However, most adventurers do not take whistling just for the entertainment value. Instead, they are looking for its uses in communication. This communication is possible only among those who know this proficiency. If both characters succeed with their proficiency checks, a single concept can be communicated. Some examples are "Go around to the side door," "I hear them coming," "Slowly reach out now, the guard doesn't see you."

[Complete Bard's Handbook]