Does anyone know of a program that can tell you what frequencies are being played? Winamp has the display in the upper left, but it doesn't display the frequency. I'm particularly interested in the bass region. I'd like to see just how low some of the bass goes in many songs. Then over in car audio world we can see that we don't really need to hit 20hz. We can see how low we really need to go.

Thank you very much!

This program is fun. 30hz sine waves really rumble. My computer sub is rated to 25 hz, but it doesn't like high volumes below 30. From 10 feet away, it feels like there's a fan blowing on my feet from the port.