Gmail has a built-in player for MP3 attachments. If you receive emails that include MP3 files (maybe a podcast or a public domain recording), you can listen them directly from Gmail. This is similar to the player used for voicemails from Google Talk.

You can create a new filter for MP3 files, so it's easier to find them. You need to add a new label. You can check how it works, just append the following URL of an MP3 file to:

http://mail.google.com/mail/html/audio.swf?audioUrl=LINK TO YOUR MP3

If you want to add Gmail player (like above) to your site just paste the following code:

<iframe src="URL to MP3 File -like e.g. above" style="width: 500px; height: 25px; border: 1px solid #aaa;" id="musicPlayer"></iframe>

You can also replace above podcast with an MP3 URL of your choice:

<script type="text/javascript"></script>
<p>
<div><input type="text" id="musicSource" size="50" style="font-size: 90%" value="http://www.itconversations.com/audio/download/podcastacademy-1090.mp3" /><input type="button" value="Replace" onclick="replaceUrl()" /></div></p>

Source:→  googlesystem | Philipp Lenssen - For update