The GFI System Rossie offers three core filter modes: The Envelope Filter delivers classic funk and auto-wah sounds, controlled traditionally by the instrument's velocity. The Step Filter mode creates rhythmic filter arpeggios with adjustable steps, while the Manual Filter allows precise sound shaping, cocked wah effects, and custom wah tones using an external expression pedal. Each mode features four filter types: lowpass, bandpass, highpass, and peak with unlimited control over sweep range and effect intensity.