This repository is based on the work of robsoncouto. I modified some of their code and added more Christmas songs.
Melodies are limited to one or two verses.
The sketches do not rely on any external libraries, only the built-in tone() function. It uses pulse width modulation (PWM) to create a square wave at a particular frequency to emulate music notes. Most Arduino boards have several PWM-capable pins. Choose one and remember to define BUZZERPIN at the top of the sketch.
You can use an active buzzer, passive buzzer, or speaker. Different components will require different wiring. I used a 5V active buzzer wired as shown below. You must use a current-limiting resistor to avoid drawing too much current from the Arduino's GPIO pin. Larger resistor values will produce a quieter sound. I found a 470 Ω resistor worked best but it will depend on the component and your preference. Anything larger than 220 Ω should be safe to use with an Arduino Uno or Nano.
You can add new songs by translating sheet music and following the pattern in the examples. Since there is only one buzzer you can think of it like playing a piano with one finger. It's helpful to use simple arrangements that play one note at a time.
Quarter notes are given a value of 4, half notes are 2, and so on. Dotted notes are multiplied by -1. Use the clef diagram below to translate.
You may find that adding more than four or five melodies to a single sketch will cause an Uno or Nano to crash and reboot. This is because of the limited available RAM. You could modify sketches to store melody arrays in PROGMEM or look at using boards with more RAM like the Nano Every or Teensy. I included a progmem_example to show how it can be done. This sketch plays 12 songs and only uses 28 bytes (1%) of dynamic memory on a Nano.