Steven Wilson uses it alot, its the one where it sounds like its coming through a telephone.
I think you're referring to just basic filtering via equalisation.
You cut out all the lower end of the voice and just leave the mid-upper frequencies and ta-da, it sounds like you're on the telephone.
Audio programs often have various preset options under their Equalisation functions, there's usually a "Telephone" or "Radio" preset available.
Bandpass is simply a type of EQ, just like shelving/peak/etc. Not entirely sure what you meant with that post.
