Should be simple I hope. I think I'll even take a crack at it. In the meantime, can someone whip up a script wherein:

The player plays a specific whistle item that the script checks for on the trigger flag. Player input is disabled while a solid FFC vibrates, plays a sound, then starts to move as it plays another sound. It moves a certain distance at a certain speed and plays a third and final sound when it stops, after which player input is restored. Then the FFC stops being solid and becomes overhead. The FFC remains permanently open.

D0 First of three sequential SFX
D1 X distance
D2 Y distance
D3 X Speed
D4 Y Speed
D5 Whistle item #. (My quest uses multiple for different songs.)
D6
D7

This all kind of hinges specifically on whether or not it is possible to check that a SPECIFIC whistle item has been played. Or to put it in layman's terms, a specific song is required.