Extant

Extant takes up to 16 stereo inputs and a rule specifying how many active inputs at most, at least, or exactly there should be and either outputs them all (summed) or nothing. This functionality is destined to augment an upcoming module, so if it seems oddly specific, it is. But as human creativity never ceases to amaze, perhaps it can find uses I couldn't imagine. Or not. Either way, it's free!