Scope-b

We don't talk about Scope-a.

A pass-through oscilloscope effect. It watches the signal in the FX slot and draws it on
its own screen; the audio itself is unchanged.

encoder	function
blue	retrig type: auto, asc, desc, inst
green	vertical range: 0 .. 48 dB below full scale (display gain)
white	horizontal length: 20 Hz .. 4 kHz (one period of this frequency fills the screen)
red	hold: turn past halfway to freeze the trace, back to run; press the red encoder to toggle the latch

auto triggers on the most recent zero crossing of either slope, asc on a rising crossing,
desc on a falling crossing, and inst simply shows the latest samples without triggering.
A small deadband keeps noise around zero from retriggering the trace. While hold is on (red knob past
halfway or red encoder latched) the trace and its settings are frozen; release hold to resume.

The screen has a small settings strip at the top, a 4 x 4 grid and the waveform in the main area.