Peff points out here that the Scream4 'tape' algorithm has an effect of inverting the output waveform at lower frequencies. This can have the effect of canceling with the original signal if mixed back (e.g. as a Send Effect). He posts a couple of solutions and a good example that illustrates this "feature".
I have seen many examples where the tape algorithm is used on drums - this is definitely something to keep in mind if you're not using it purely as an insert.
I did my own test with an Oscilloscope application, listening on my sound-card's "stereo mix" or "What U Hear" channel, and as you can see in Figure 1, mixing the 'taped' signal with the original (blue) cancels out a huge part of the original signal (red). Only the higher frequencies remain.
My test RNS file is here.