DAFX: Digital Audio Effects, Second Edition

12.4 Electromechanical Effects

A rather special family of audio effects consists of those which employ mechanical elements in conjunction with analog electronics—though many classic effects rely on such components (such as, for example, the Leslie speaker, or tape delays), for some problems in the world of virtual analog, an involved treatment of the mechanical part of the effect is necessary, in order to be able to capture the perceptually salient quality of the effect. This is particularly the case for electromechanical artificial reverberation, which exhibits an extremely complex response. Two interesting cases, namely plate and spring reverberation, will be briefly described here.

The attribute of these devices which distinguishes them from other electromechanical effects is that the mechanical components cannot be modelled as “lumped” structurally, a spring or a plate occupies space, and its vibration pattern varies from one point to the next. It is precisely the distributed character of these components which gives these effects their complex sound—and which, at the same time, requires a somewhat different approach to emulation. One must now think of the behavior of the component in terms of various different modes of vibration, or in terms of waves which require finite propagation times, just like real acoustic spaces. Indeed, spring and plate reverbs were originally intended as convenient substitutes for real room reverbs—but developed a loyal audience of their own. Originally, ...