The size of the FFT depends on the selected duration. Input Source Microphone, Line, or Soundfile. If the latter, then a Motif FileSelectionBox is displayed. Input Channel Left or Right. If Envelope is selected then two lines are displayed joining max and min amplitude values.
V puts the cursor on the lower envelope.
Sample Rate input sample rate. May slow things up a bit and can filter out very low frequencies. Display can have all or any of Time Waveform, Spectrum, Spectrogram, or Waterfall. In Envelope mode, max and min curves are listed consecutively. In zoom in to selected range or decrease frequency axis range by a factor of 2.