Learning   Examples | Foundations | Hacking | Links

Examples > Digital I/O

Pitch follower using the tone() function

This example shows how to use the tone() command to generate a pitch that follows the values of an analog input

Hardware Required

  • 8-ohm speaker
  • 1 photocell
  • 4.7K ohm resistor
  • 100 ohm resistor
  • breadboard
  • hook up wire


image developed using Fritzing. For more circuit examples, see the Fritzing project page

Connect one terminal of your speaker to digital pin 9 through a 100 ohm resistor, and its other terminal to ground. Power your photoresistor with 5V, and connect it to analog 0 with the addition of a 4.7K resistor to ground.


click the image to enlarge


The code for this example is very simple. Just take an analog input and map its values to a range of audible pitches. Humans can hear from 20 - 20,000Hz, but 100 - 1000 usually works pretty well for this sketch.

You'll need to get the actual range of your analog input for the mapping. In the circuit shown, the analog input value ranged from about 400 to about 1000. Change the values in the map() comand to match the range for your sensor.

The sketch is as follows:

  Pitch follower
 Plays a pitch that changes based on a changing analog input
 * 8-ohm speaker on digital pin 8
 * photoresistor on analog 0 to 5V
 * 4.7K resistor on analog 0 to ground
 created 21 Jan 2010
 modified 30 Aug 2011
 by Tom Igoe

This example code is in the public domain.

void setup() {
  // initialize serial communications (for debugging only):

void loop() {
  // read the sensor:
  int sensorReading = analogRead(A0);
  // print the sensor reading so you know its range
  // map the pitch to the range of the analog input.
  // change the minimum and maximum input numbers below
  // depending on the range your sensor's giving:
  int thisPitch = map(sensorReading, 400, 1000, 100, 1000);

  // play the pitch:
  tone(9, thisPitch, 10);


See Also:

  • Array()
  • for()
  • tone()
  • map()

  • Tone - play a melody with a piezo speaker
  • SimpleKeyboard - a three-key musical keyboard using force sensors and a piezo speaker.
  • Tone 4 - play tones on multiple speakers sequentially