 <p>Added my comment as an answer:</p> <p>You might want to look into the HTML5 Audio Data API. Other than that, you're going to need Flash if you want a legit spectrum analyzer (which, by the way, is what you're asking for. not an equalizer). </p> <p>Edit:</p> <p>For anyone interested, I have a quick and dirty demo here: <a href="http://kevincennis.com/audio/" rel="nofollow">http://kevincennis.com/audio/</a> (Chrome only)</p> <p>Source is un-minified, but not particularly well commented. Feel free to steal whatever you want.</p>