gpiozero button issue with is_held

I am making a pumpkin pi for Halloween and am having trouble with the integration of the button; specifically, the is_held bit. It consists of 3 led lights that make up the candle (1 yellow flicker, 1 yellow "breathing", and 1 orange steady) and a red led light that fades in as the candle fades out, then pulses with creepy laugh. I have integrated the button to start everything, but when I hold the button down to stop it, nothing happens. I am pretty new to coding, so any help regarding my main issue or feedback in general is appreciated!

from gpiozero import PWMLED, Button
from gpiozero.tools import random_values
from signal import pause
from time import sleep
import subprocess
import random

led_flicker_yellow = PWMLED(17, frequency = 1500)
led_breath_yellow = PWMLED(18, frequency = 1500)
led_steady_orange = PWMLED(27, frequency = 1500)
led_red = PWMLED(24, frequency = 1500)
button = Button(2, hold_time = 2)


def candle_lights():
    led_flicker_yellow.source = random_values()
    led_flicker_yellow.souce_delay = random.uniform(0.05,0.1)
    led_breath_yellow.pulse(15,10)
    led_steady_orange.value = 0.20

def candle_out():
    led_flicker_yellow.source = led_pulse_yellow
    led_breath_yellow.pulse(0,3, n=1)
    led_steady_orange.off()

def pumpkin_pi():                      
    subprocess.Popen (["omxplayer", "-o", "alsa", "--loop", "/home/pi/Desktop/LED_PROJECTS/SoundEffects/candle.mp3"])
    while True:
        candle_lights()       
        sleep(300)
        candle_out()
        subprocess.Popen(["omxplayer", "-o", "alsa", "/home/pi/Desktop/LED_PROJECTS/SoundEffects/laugh.mp3"])
        led_red.pulse(3,0,n=1)
        sleep(3)
        led_red.blink(0.03,0.03,n=35)
        sleep(2)
        candle_lights()
        if button.is_held:
            subprocess.call(["pkill", "omx"])
            break

button.when_pressed = pumpkin_pi

Ok - so credit to thagrol on RPi forums, but here is the answer. Here I am controlling an LED light sequence that utilizes a while True loop with a button via python and gpiozero.

from gpiozero import PWMLED, Button
from time import sleep 
from signal import pause
import threading

led = PWMLED(24)
button = Button(2, hold_time=2)

running = False

def pumpkin_pi_loop():
    while running:
        led.value = 0 
        sleep(1)
        led.value = 0.5
        sleep(1)
        led.value = 1
        sleep(1)
        
def button_press():
    global running
    if not running:
        led.value = 1
        sleep(3)
        running = True
        loop_thread = threading.Thread(target=pumpkin_pi_loop, daemon=True)
        loop_thread.start()
    else:
        running = False

def button_hold():
    global running
    running = False

button.when_pressed = button_press
button.when_held = button_hold


pause()