[Post Processing Script to add sound to Gcode]

I am trying to write a python script to play subsequent beeps at the end of a print so i can hear when it's done. I have already got it to show up in Cura (a feat on its own), and now I'm trying to make the script run like I want it to. Here is the script:

 

# SEEKMSMSMSM
# Script to play beeps

from typing import List, Dict
from ..Script import Script
import re

class Soundy(Script):
    version = "1.0.0"

    def getSettingDataString(self):
        return """{
            "name": "Soundy",
            "key": "Soundy",
            "metadata": {},
            "version": 2,
            "settings":
            {
                "startFreq":
                {
                    "label": "Start Frequency",
                    "description": "The starting value of the sound.",
                    "type": "int",
                    "default_value": 300
                },
                "endFreq":
                {
                    "label": "End Frequency",
                    "description": "The ending value of the sound.",
                    "type": "int",
                    "default_value": 800
                },
                "individualDuration":
                {
                    "label": "Individual Sample Duration",
                    "description": "How long should each frequency between the range play?",
                    "type": "int",
                    "default_value": 1,
                    "minimum_value": 0.2,
                    "maximum_value": 20,
                    "maximum_value_warning": 15
                }                
            }
        }"""

    def __init__(self):
        super().__init__()

    def execute(self, data):

        StartFreq = self.getSettingValueByKey("startFreq")
        EndFreq = self.getSettingValueByKey("endFreq")
        ID = self.getSettingValueByKey("individualDuration")
        sound = range(StartFreq,EndFreq)
        Command = "M300"
        for n in sound:
            SoundCode = str(Command," P",ID," S",n,sep='')
            
        for layer in data:
            index = data.index(layer)
            layer = layer + "\n" + SoundCode
            data[index] = layer
            return data
            break
                        
        return data
        
The script shows up, shows the values I can edit, then when I check the Gcode, there's non of the commands I want (M300 P1 S500, for example)