What does it mean?
A compressor reduces level around the threshold according to its curve and ratio. A gate attenuates low-level sound; Auto Swell uses a threshold to open a fade. These processes act differently.
ExampleA gate threshold set too high cuts off the end of a sustained note.
How the meaning changes between controls
Noise Gate
The input-level boundary for opening and closing the gate.
Compressor
The reference level around which compression begins, according to knee and ratio.
Auto Swell
The envelope level that opens the swell; this is not a musical note detector.