Hi,

I'm trying to make a circuit with a low pass, and high pass filter. I don't know how to vary the band pass though. Any help?

 

Have you made a circuit? if yes post the diagram.
Do you want to make a passive filter or an active filter?

 

And do you know what an active filter is? (Hint, its a powered circuit).

Tell us what you need, you'll get lots of help.