Here is code of Google Reader Player to put on your blog. The code above looks like the below.
|<embed type="application/x-shockwave-flash" flashvars="audioUrl=Url Of Your Mp3 File" src="http://www.google.com/reader/ui/3523697345-audio-player.swf" width="300" height="30" quality="best" wmode="transparent"> </embed>|
And by the way, there are also many free services that provide lots of songs that which you can take advantage of the url to play music on your blog, so you don't have to upload any mp3 file yourself. Here is one: http://www.singingbox.org/index2.php