Dual Band Selector

The Logic-style "Low Cut … High Cut" band bar: two caps on one log or linear frequency track with the band between them lit. Press the band to move both caps at their current width, press the open track to jump the nearer one, Shift for a fine pass, wheel and arrows on the focused cap. The caps stop against each other at a minimum ratio (log) or difference (linear) instead of crossing, and the taper, the gap and the band drag are a pure core with its own tests.