I have created a [url=http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=17.msg114#msg114]Fourier Synthesis[/url] in 1999.
Here is the EJS version of Fourier Synthesis.
You can adjust the Fourier component with the slider and watch the wave change at the same time.
Click "play" to hear the sound.