Add + Gain is a control-math block that sums two control signals and scales the result. It takes two control inputs and produces one control output — there is no audio path — and a single Gain parameter (0 to 1, default 1) multiplies the sum before it leaves the block.
Each tick it adds the two control-input values together and multiplies the total by the Gain, writing the product to the control output. It processes one sample-frame per tick, in step with WaveWarp's sample-per-sample engine.