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Tone Library


This is an Arduino Library to produce square-wave of the specified frequency (and 50% duty cycle) on any Arduino pin.

A duration can optionally be specified, otherwise the wave continues until stop() is called.

The pin can be connected to a piezo buzzer or other speaker to play tones.

Be sure to try out the RTTTL (RingTone Text Transfer Language) example!

Arduino Core Version

A simplified version of the Tone library has been incorporated into the Arduino core since 0018. It only provides a single tone (since only one timer is used). You can find the core documentation here.

Check out the tutorial by Tom Igoe at NYU's Interactive Telecommunications Program (ITP). It demonstrates how to use the core tone() and noTone() commands.


Do not connect the pin directly to some sort of audio input. The voltage is considerably higher than a standard line level voltages, and can damage sound card inputs, etc. You could use a voltage divider to bring the voltage down, but you have been warned.

You MUST have a resistor in line with the speaker, or you WILL damage your controller.

Download and Installation

Unzip the folder and rename it to Tone, then move it to your arduinosketchfolder/libraries/ folder.

Hardware Connections/Requirements

  • Just connect the digital pin to a speaker (with a resistor - say 1K - in line), and the other side of the speaker to ground (GND).
Tone-Arduino-Connections Tone-Wiring-Connections
  • You can use a potentiometer to control the volume. Use a 10K Ohm potentiometer (variable resistor) in line with the 1K Ohm resistor connected to the speaker.

  • Using this library will affect usage of the PWM outputs, so be aware.

  • Also, although it's the last timer to be allocated, timer 0 (which is used for millis() among other things) will be affected if used.

Library Usage


Tone tone1;

void setup(void)


  • No properties.


  • begin(pin) - prepares a pin for playing a tone.
  • isPlaying() - returns true if tone is playing, false if not.
  • play(frequency[,duration]) - play a tone.
    • frequency is in Hertz, and the duration is in milliseconds.
    • duration is optional. If duration is not given, tone will play continuously until stop() is called.
    • play() is non-blocking. Once called, play() will return immediately. If duration is given, the tone will play for that amount of time, and then stop automatically.
  • stop() - stop playing a tone.


Below is a list of constant values of frequencies for notes. (These are included in the library).


Musical Notes

Constant Name Frequency (Hz)
NOTE_B0 31
NOTE_C1 33
NOTE_D1 37
NOTE_E1 41
NOTE_F1 44
NOTE_G1 49
NOTE_A1 55
NOTE_B1 62
NOTE_C2 65
NOTE_D2 73
NOTE_E2 82
NOTE_F2 87
NOTE_G2 98
NOTE_GS2 104
NOTE_A2 110
NOTE_AS2 117
NOTE_B2 123
NOTE_C3 131
NOTE_CS3 139
NOTE_D3 147
NOTE_DS3 156
NOTE_E3 165
NOTE_F3 175
NOTE_FS3 185
NOTE_G3 196
NOTE_GS3 208
NOTE_A3 220
NOTE_AS3 233
NOTE_B3 247
NOTE_C4 262
NOTE_CS4 277
NOTE_D4 294
NOTE_DS4 311
NOTE_E4 330
NOTE_F4 349
NOTE_FS4 370
NOTE_G4 392
NOTE_GS4 415
NOTE_A4 440
NOTE_AS4 466
NOTE_B4 494
NOTE_C5 523
NOTE_CS5 554
NOTE_D5 587
NOTE_DS5 622
NOTE_E5 659
NOTE_F5 698
NOTE_FS5 740
NOTE_G5 784
NOTE_GS5 831
NOTE_A5 880
NOTE_AS5 932
NOTE_B5 988
NOTE_C6 1047
NOTE_CS6 1109
NOTE_D6 1175
NOTE_DS6 1245
NOTE_E6 1319
NOTE_F6 1397
NOTE_FS6 1480
NOTE_G6 1568
NOTE_GS6 1661
NOTE_A6 1760
NOTE_AS6 1865
NOTE_B6 1976
NOTE_C7 2093
NOTE_CS7 2217
NOTE_D7 2349
NOTE_DS7 2489
NOTE_E7 2637
NOTE_F7 2794
NOTE_FS7 2960
NOTE_G7 3136
NOTE_GS7 3322
NOTE_A7 3520
NOTE_AS7 3729
NOTE_B7 3951
NOTE_C8 4186
NOTE_CS8 4435
NOTE_D8 4699
NOTE_DS8 4978

Quick example

Play a 440 Hz - musical note of 4^th^ octave A - on pin 13:

#include <Tone.h>

Tone tone1;

void setup()

void loop()

Ugly Details

The library uses the hardware timers on the microcontroller to generate square-wave tones in the audible range.

You can output the tones on any pin (arbitrary). The number of tones that can be played simultaneously depends on the number of hardware timers (with CTC capability) available on the microcontroller.

  • ATmega8: 2 (timers 2, and 1)
  • ATmega168/328: 3 (timers 2, 1, and 0)
  • ATmega1280: 6 (timers 2, 3, 4, 5, 1, 0)

The timer order given above is the order in which the timers are allocated. Timer 0 is a sensitive timer on the Arduino since it provides millis() and PWM functionality.

The range of frequencies that can be produced depends on the microcontroller clock frequency and the timer which is being used:

MCU clock 8 bit timer Flow 16 bit timer Flow Fhigh
8 MHz 16 Hz 1 Hz (1/16 Hz) 4 MHz
16 MHz 31 Hz 1 Hz (1/8 Hz) 8 MHz

Although Fhigh can go as high as 8 MHz, the human hearing range is typically as high as 20 kHz.

Tone accuracy is dependent on the timer prescalar. Frequency quantization occurs as the frequencies increase per prescalar.

If you used a 16 bit timer (e.g. timer 1, or timers 3,4,5 on '1280), you could generate "tones" down to 1/8 Hz (one cycle every 8 seconds), although the library only accepts integers for frequency.

After all is said and done, because play() only accepts unsigned integers for frequency, the maximum frequency that can be produced is 65535 Hz - which, after rounding, results in a 65573.77 Hz "tone" on a 16 MHz part. Even if play accepted larger values for frequency, you couldn't achieve better than around 80KHz with the Tone library because the pin toggling is done in software. Each toggle, in software, requires AT LEAST 50+ cycles.


Projects/Examples Using Tone Library and Wiring Framework Version of tone()




A Wiring Library to produce square wave tones on arbitrary pins.







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