Arduino library to play MML music using a piezo speaker on an output pin. Implemented using the MmlMusic base library.

MmlMusicPWM provides a means to play Music Macro Language sequences asynchronously. Where the Arduino tone() function allows for playing one single note, the MmlMusicPWM::play() method can play an entire music score.
It produces sound by means of a PWM signal on an output pin, which can be connected to a piezo speaker, or via an amplifier to a regular speaker. The music is played using a timer interrupt routine that changes the PWM frequency according the specific notes being played. This means we can do other things while the music keeps playing!

This library is an extension to the MmlMusic base library. It is implemented as a child class of the device independant MmlMusic class. That class requires additional code via either a callback function or the implementation of a child class to implement the actual production of sound.

This library supports playing MML music on different MCUs such as ESP8266, ATmega 328, 168 and ATtiny85. Depending on the MCU, it uses different timers and interrupts to produce the sound and to schedule playback of notes and silences. The music will keep on playing using a timer interrupt. On the ESP8266 the Ticker library is used. For ATmega 328/168 a Timer2 interrupt is used and a replacement method for tone() is provided. On the ATtiny85 resources are limited. There a Timer1 interrupt is used, which impacts regular PWM output.
BTW: The MmlMusic Tone example shows how to play notes without using a timer interrupt.

The library can be downloaded and installed as an Arduino library using the Sketch|Library menu. Just add the zipfile library and the enclosed examples should appear in the menu automatically.

Initialisation outside of Setup():

  // include header and initialize class
  #include <MmlMusicPWM.h>
  MmlMusicPWM music();

Then to play music, call the play method where you want:

music.play("T240 L16 O6 C D E F G");

When playing the rest of the sequence, the isPlaying() method can be used to determine if the sequence is still playing.

if(music.isPlaying()
{
    ...
}

Alterternatively a callback function can be used to signal the start or end of playing the tune. See the included examples for more detailed instructions on how to use this library.

Short syntax overview:

The supported MML-commands are a subset that may not completely cover all available music scores. If notes seem missing, check your score against the syntax above and replace unknown commands by equivalent supported alternatives. The music notation is case-insensitive. Spaces are not required but can be used for readability.

• Playing back multiple tracks is supported by the base library, but not (yet) by this library. Only a single pulse-stream is generated. The documentation of the comma-command above is maintained for future purposes.
• This library was tested in the Arduino IDE v1.6.10 and v1.8.2. The current version of this library supports ESP8266, Atmel ATmega328 and ATmega168 MCUs. Support for ATtiny85 was also added, but since the ATtiny85 has limited resources, available memory limits it usage to simple applications. On ATtiny85 Timer1 is used, impacting the use of the regular PWM analogWrite() function.
• There was a bug in the MmlMusic base library that could impact playback of notes and the duration of the delay() function. When ending the play-string with a number (eg. "T120 O4 G16"), the player could read beyond the end of the string, play whatever was next in memory and mess up the timer callback. This bug has been fixed. Please use the latest version of the MmlMusic base library. See this issue for details.
• In ESP8266 cores 2.5.1 and higher reading a float array from PROGMEM had a byte alignment issue causing incorrect playback of notes. This issue was fixed in ESP8266 core 2.6.0 and has a workaround in the MmlMusic base library for earlier cores. See this issue for details.

The base library is based on the MusicEngine library by Chris Taylor, ported from mBed to Arduino. It is a follow-up of the ESP-MusicEngine library.

• Learn more about Music Macro Language (MML) on wikipedia:
  http://en.wikipedia.org/wiki/Music_Macro_Language
  
• For downloadable MML music see http://www.archeagemmllibrary.com/
  
• Extensive MML reference guide (not all commands supported):
  http://woolyss.com/chipmusic/chipmusic-mml/ppmck_guide.php
  
• Info about using PWM and other methods to generate sound:
  https://developer.mbed.org/users/4180_1/notebook/using-a-speaker-for-audio-output/

• All code on this GitHub account, including this library is provided to you on an as-is basis without guarantees and with all liability dismissed. It may be used at your own risk. Unfortunately I have no means to provide support.