Square is by far the simplest wave shape for a digital processor to produce, as we saw it the last chapter, it was a simple matter of setting a digital pin high and then setting it low or on and off. Also we saw when mixing two such waves a third intermediate level appeared, one that was halfway between high and low. This occurred when one signal was high and the other was low. The trick to producing other wave shapes and therefore different sounding noises is to have some mechanism to generate not only one intermediate level between high and low but many. The more levels you can generate, the finer precision you can sculpt your waveform.