Recorder

A Warp Whistle is an item from Super Mario Bros. 3. Using it sends Mario (or Luigi) to the Warp Zone. From here, he can skip up from the middle of a world to the start of a later world. Using it in World 1 will allow Mario to warp to World 2, 3, or 4. Using it in a world from 2 through 6 will allow him to warp to World 5, 6, or 7. Using it World 7 or 8 will allow him to warp to World 8. If a second whistle is used while in the warp zone, then the player is taken directly to the World 8 Pipe.

There are only 3 whistles in Super Mario Bros. 3:

World 1-3
Obtained by falling through (holding down on the control pad while standing on it) the last white block in the level and making Mario's way to the end of the stage while behind the scenery.

World 1 Fortress
Obtained by flying above the level at the very end of the first area. Start all the way on the right side past the door and run to the left, taking off at the last second. While flying off-screen, direct Mario to the platform above the door below. When at the end of the platform hit up and Mario will be warped to a room with a tresure chest containing the second Warp Whistle.

World 2 Secret Fire Bros. Brigade
Obtained by using a Hammer on the rock in the upper right corner of the map. Destroy the Fire Bros. to win it.

World 5-1 (Japanese Version)
In the Japanese version of Super Mario Bros 3, when you go through the pipe at the end of the level, you will come out at the ending, with a wall behind you. If you are a raccoon, fly up the wall until you get to the top. Once there, you will here a sound like the one played when a treasure chest appears. Now, come down! When you go to the ending, there is another flashing item on the ground(5 UP and warp whistle.) If you time it right, you will hit the warp whistle with your tail. Then, after you hit the roulette box, there is a treasure chest that appears. When you run into it, you will acquire either a 5 UP or a fourth and final warp whistle.

Trivia

 * Mystical Whistle is the name of a Sammer Guy in Super Paper Mario is a pun on Warp Whistle.
 * The song played by the Warp Whistle is from The Legend of Zelda series.
 * A reference to the Warp Whistle is made in the Nintendo Monopoly.
 * Another flute is found in the game Mario is Missing!, stolen from the Teatro Colon by Koopa Troopas. Luigi had to return it to the opera house.