How to do it...

Let's perform the following steps:

1. Run the following lines of code in the REPL. You should hear a high-pitched beeping sound for 0.5 seconds:

>>> from adafruit_circuitplayground.express import cpx
>>> import time
>>> 
>>> BEEP_HIGH = 960
>>> BEEP_LOW = 800
>>> 
>>> cpx.pixels.brightness = 0.10
>>> cpx.start_tone(BEEP_HIGH)
>>> time.sleep(0.5)
>>> cpx.stop_tone()

1. Use the following code to play a beeping sound in the background while 10 pixels turn red at 0.1-second intervals. The beeping will then stop at the end of the animation:

>>> cpx.start_tone(BEEP_HIGH)
>>> for i in range(10):
...     cpx.pixels[i] = 0xFF0000
...     time.sleep(0.1)
... 
>>> cpx.stop_tone()
>>> 

1. Use the following block of code to perform a similar operation, but with a lower pitch. Here, the pixel animation will turn off each pixel one by one, ending the tone at the end of the animation:

>>> cpx.start_tone(BEEP_LOW)
>>> for i in range(10):
...     cpx.pixels[i] = 0x000000
...     time.sleep(0.1)
... 
>>> cpx.stop_tone()
>>> 

1. The code that follows combines all the code shown in this recipe to make one complete program. Add this to the main.py file and it will play a siren alarm and animate the pixels on and off with the siren:

from adafruit_circuitplayground.express import cpx
import time

BEEP_HIGH = 960
BEEP_LOW = 800

cpx.pixels.brightness = 0.10

cpx.start_tone(BEEP_HIGH)
for i in range(10):
    cpx.pixels[i] = 0xFF0000
    time.sleep(0.1)
cpx.stop_tone()

cpx.start_tone(BEEP_LOW)
for i in range(10):
    cpx.pixels[i] = 0x000000
    time.sleep(0.1)
cpx.stop_tone()