Upside down. When dealing with audio signal levels, 0dB is “full volume” and signals lower than this are negative values. Absolute silence is “negative infinity” dB.
The tempo is not directly the “cause” that triggers the effect. “Gater” is a kind of “Noise Gate” effect, which is triggered by the amplitude (level) of the audio. When the audio is above a specified level, the gate opens and allows the sound through, when the audio falls below that level, the gate closes and mutes the sound.
I’m well aware that tempo doesn’t “trigger” the gate, but it’s not a noise gate that I’m looking for. The GB Gater doesn’t work like the Noise Gate; it’s something that takes effect when the user puts their finger somewhere on that slider. Then, during recording over the existing music, GB takes that input, processes it, and applies it as a seperate FX layer that can be moved or adjusted.
Normally you would install a Nyquist Plug-in, and then launch it from the appropriate menu (Generate, Effect, Analyze or Tools) in the same way as you would launch a built-in effect. By default, plug-ins are listed at the bottom of the menus.