A linear-phase FIR filter designed by the windowed-sinc method. Pick a Response — lowpass, highpass, bandpass or bandstop — and a Window (Hann, Hamming or Blackman) that trades transition width against stopband depth. Taps sets the filter length (15 to 511: more taps give a sharper transition at higher CPU cost), Frequency the corner or centre, and Bandwidth the width of the band for the bandpass and bandstop responses. Because the impulse response is symmetric, the filter has exactly linear phase — all frequencies are delayed equally, which keeps transients intact and is often preferred for audio. The filter adapts automatically to the incoming signal's sample rate.
An ideal sinc impulse response for the chosen response and cutoff is truncated to the tap count and multiplied by the selected window; the result is applied by direct convolution, advancing one sample-frame per tick to stay inside WaveWarp's sample-per-sample engine. Every parameter change re-derives the taps.