Yamaha isn't giving much detail, but we think that it is similar to the ToneDexter preamp. A convolution function (a mathematical operation on two functions that produces a third function expressing how the shape of one is modified by the other) is created by playing an acoustic instrument, recording the sound with the piezo pickup to be used and a high-quality microphone. Essentially, the expected difference between the two waveforms is computed in advance and applied to the piezo pickup sound in order to approximate the microphone sound. It is not like a digital keyboard that stores sound samples, it's more like a digital tone control that guesses what the microphone would have picked up. It has to do some serious computation while it's running, which is why two AA batteries don't last nearly as long as they did in the previous version of the Silent Bass. Presumably, Yamaha builds the convolution function using a real live double bass equipped with a piezo pickup similar to the one in the SLB300.