Every sound can be represented in the so-called 'frequency domain'. This means that we can look at a sound as being a collection of frequency 'components' at different amplitudes. If we then plot this on a graph, called a spectrogram, we can get something like this:

If we make multiple analyses at a given interval, however, and 'interpolate' or 'inbetween' those analyses, we get a blurring effect, where the small-scale frequency changes are lost, and instead become slow-changing 'inharmonic spectra' (like a bell):

NB: (This effect owes its conception to Mr. Trevor Wishart - a British freelance composer, programmer and theorist. His book Audible Design (which I strongly recommend), was the inspiration for many of the implementations in the SoundMagic FX suite. Unfortunately, the Composers Desktop Project, of which Mr. Wishart was part, was unavailable for the Macintosh. I hope that SoundMagic goes some way toward remedying that problem.)

Window length: The distance between analysis points. As you can see in the above plot, the window length is quite visible, and at long times, audible as a sort of 'pulsing' effect. Shorter time values, however, just tend to 'phase' the sound in an interesting manner. The key here is to experiment.