PM1

PM1 is a container format used for the PS2 versions of Persona 3 and Persona 4. related to in-game events.

They often contain various resources used in the event, such as the dialogue script. There isn't a fully fledged editor for this format yet, however there is a tool that can be used to extract & insert the dialogue script.

PM1MessageScriptEditor
Drag a PM1 file onto the PM1MessageScriptEditor exe to extract a .msg (messagescript), edit it with your text editor of choice, and drag it onto the exe when you're done. This will replace the embedded BMD in the PM1 without recompiling the event itself.