from machine import Pin, PWM
from time import sleep
buzzer = PWM(Pin(25))

buzzer.duty(1000) 

# Happy birthday
buzzer.freq(294)
sleep(0.25)
buzzer.freq(440)
sleep(0.25)
buzzer.freq(392)
sleep(0.25)
buzzer.freq(532)
sleep(0.25)
buzzer.freq(494)
sleep(0.25)
buzzer.freq(392)
sleep(0.25)
buzzer.freq(440)
sleep(0.25)
buzzer.freq(392)
sleep(0.25)
buzzer.freq(587)
sleep(0.25)
buzzer.freq(532)
sleep(0.25)
buzzer.freq(392)
sleep(0.25)
buzzer.freq(784)
sleep(0.25)
buzzer.freq(659)
sleep(0.25)
buzzer.freq(532)
sleep(0.25)
buzzer.freq(494)
sleep(0.25)
buzzer.freq(440)
sleep(0.25)
buzzer.freq(698)
sleep(0.25)
buzzer.freq(659)
sleep(0.25)
buzzer.freq(532)
sleep(0.25)
buzzer.freq(587)
sleep(0.25)
buzzer.freq(532)
sleep(0.5)
buzzer.duty(0)