Yeah that. Portcullis.

Basically you use a specific whistle item, then everything freezes (or at least player input is turned off for the duration) after the sound ends.

The gate rumbles/vibrates (vertically only), then lifts upwards. The rumbling has one sfx play, the lifting has another. When the FFC stops moving a final sound plays and it stays open forever.

Oh right an optionally the MIDI stops playing (preferably it simply pauses. if that's not doable then just zeroing its volume/muting it. But if that's not doable either then just stopping and restarting it is fine)