ECS

ECS is a binary event format used by Atlus in Persona 5. It is used to store sound commands, and is to be used along with an EVT file.

Location
Persona 5's ECSs can be found in the PAC files in data.cpk\event.

EvtTool
EvtTool is a program by TGE that dumps the contents of an EVT, ECS or LSD binary to an editable JSON file, which can be opened with a text editor such as Notepad++. By dragging an EVT onto the EXE, a JSON will be generated (and vice versa). You can download EvtTool here.

Alternatively you can use the program through the commandline by passing in the file path to either an EVT or a JSON file (in case you want to batch the conversion, for example).

P5_EVT_ECS.bt
A binary template for 010 Editor can be used to study the structure of an EVT/ECS file while hex editing. Download that here.

Format
The format of an ECS consists of nothing but a command list. Like EVT, each command has its own specific parameters and a short descriptor (e.g. SND_).

Below are a list of all used commands and their functions (to the best of our knowledge).