autoplay Attribute

<audio controls autoplay>
  <source src="horse.ogg" type="audio/ogg">
  <source src="horse.mp3" type="audio/mpeg">
  Your browser does not support the audio element.
</audio>

how to autoplay a music with html5 embed tag while the player is invisible

<audio autoplay loop>
      <source src="johann_sebastian_bach_air.mp3">
</audio>

<audio src="music/file.mp3" autoplay="autoplay"></audio>

<audio src="music/file.mp3" autoplay="autoplay" loop="loop"></audio>

<audio autoplay="autoplay" loop="loop">
<source src="music/MP3file.mp3" type="audio/mpeg">
<source src="music/OGGfile.ogg" type="audio/ogg">
</audio>

Read more : http://www.ehow.com/how_8442990_add-background-html-music-code.html

How To Make The Audio Player Autoplay

<audio controls autoplay>
  <source src="https://s3.amazonaws.com/Syntaxxx/bigger-picture.mp3" type="audio/mpeg">
  <p>If you can read this, your browser does not support the audio element.</p>
</audio>

<audio controls autoplay>
  <source src="music.mp3" type="audio/mpeg">
  <source src="music.ogg" type="audio/ogg">
  <source src="music.wav" type="audio/wav">
  <p>If you can read this, your browser does not support the audio element.</p>
</audio>

http://www.syntaxxx.com/html5-audio-autoplay-automatically-play-audio-on-your-website/