The 3 Note Piano Box lets you play 3 natural notes (F,G and A), along with 3 sharp notes, (F#, G#, and A#).

The natural and sharp notes are both played by pressing the 3 buttons along the top. By default, the natural notes play; to play the sharp notes, you cover the photoresistor at the front of the piano box with your palm.

The 3 Note Piano Box introduces the concept of polyphony and interactive state machines. While earlier buzzer projects focus on playing pre-programmed songs automatically, this project turns the Arduino into a playable musical instrument.

Multi-Button Input Reading

The challenge here lies in constantly monitoring multiple inputs without the code getting stuck.

1. The Setup: You wire three push buttons to digital pins 2, 3, 4. By utilizing the Arduino's internal pull-up resistors (pinMode(2, INPUT_PULLUP)), you can eliminate all messy external 10k resistors on your breadboard—wiring the buttons directly to Ground.
2. The Main Loop: The Arduino checks all three buttons in rapid succession (millions of times a second).
3. The Frequency Trigger:
   • if (digitalRead(button1) == LOW) { tone(buzzerPin, 261); } (Plays Middle C: 261 Hz)
   • ... (button2) -> Plays E (329 Hz)
   • ... (button3) -> Plays G (392 Hz)
4. The Silence: Critically, you must include an else { noTone(buzzerPin); } statement at the very end. Otherwise, if you let go of the button, the buzzer will scream Middle C forever!

Required Hardware

• Arduino Uno/Nano: The synthesizer core.
• Three Tactile Push Buttons.
• Active or Passive Piezo Buzzer.
• A Small Enclosure: (Optional) To mount the buttons and hide the messy wiring, creating a neat "Piano Box".

This project is the perfect stepping stone to building full 8-key octave synthesizers and learning to use the Mozzi audio generation library.

How to Build:

1: 3D print the enclosure .stl file. Make sure you put one breadboard on the top of the box, and keep the second one on a flat surface (like your table) to begin with.

2: Wire the photoresistor and the buzzer from the Arduino Uno (pinout also works for Arduino MEGA) to the breadboard that's not on the box.

3: Plug wires for breadboard on box into Arduino, but do not connect them to breadboard yet.

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4: Tape or glue second breadboard and arduino uno inside of the box (see reference images below)

5: Bring photoresistor out through the front of the box.

6: Finally, bring the wires that for breadboard on top through the hole on the top of the box and wire them to their respective locations on the breadboard.