I love those little fidget toys that sound like bubble wrap popping. I also really like to bother my friends with music that sounds like it's a phone ringtone from the 90s.

This takes a 4x4 keypad (or 4x4 button system) and each button is one note on the D Major scale (starting at C1 to G2).

Future Additions:

• Optimize code

• Long press on keypad for long note hold

• Button to switch scales

EXPANDED TECHNICAL DETAILS

Matrix-Input Musical Instrument

This project transforms a standard numeric keypad into a polyphonic-feel digital synthesizer, ideal for learning basic music theory and matrix scanning.

• 4x4 Keyboard Matrix Scanning: The Arduino uses the Keypad.h library to scan 16 tactile buttons using only 8 digital pins. The firmware maps each key to a specific musical frequency (e.g., '1' = C4, '2' = D4).
• Tone Frequency Lookup: Every keypress triggers the tone() function on a piezo buzzer. The Arduino looks up the pre-defined frequency from a chromatic scale array, providing accurate pitch reproduction.

Educational Logic

• Octave Scaling: (Advanced version) Includes a "Shift" button that allows the keypad to cycle through three different octaves, expanding the instrument's range from 16 to 48 notes.