Abbreviation for Time Variant Filter. Similar in concept to a TVA, a TVF is a filter stage that can vary its properties over time. The term TVF is often used by Roland in their keyboards and synthesizers where it replaces what is commonly just a simple filter that may or may not be triggered by some type of envelope generator. They are generally set up to have several stages or points that relate to the passage of time where the filter settings can be specified. This allows the creation of filtering effects that are automated and change as a note plays, but without having to apply any special routing or function generators to the filter.