Here’s something fun — I made a 16-step sequencer in Flash, that plays filtered noise (or sine waves, when the filter is narrow):
Drag and resize the blue blocks to change the filter frequency and width.
This sequencer is not using expensive bandpass filters. The oscillators are sine waves, which are frequency modulated with white noise. It may not sound inherently musical, but you can produce great hihats, bass thuds, and airy pitched noises.
Here’s the source code. (Requires Flash CS5 to compile.) Have fun!