Frequency analysis and additive synthesis are the conventional way to reproduce sounds in signal processing. However, digital fabrication provides an alternative way to reproduce sounds by geometrical reproduction of acoustics. This paper proposes cymatic synthesis by geometrical reproduction as an alternative to signal processing as a way to design sounds. In the other direction, cymatic synthesis can also be used to design geometric shapes from sounds. The potential of cymatic synthesis was explored through an experiment to produce a recursive series of bells, where the geometry of each bell is constructed from the spectral profile of the previous bell in the series. The knowledge gained from these experiments is captured in a process model with modular stages of SHAPE, SOUND, XFORM and PROFILE. Based on the results of the first experiment, we have designed further XFORM mappings that are more directly cymatic than the spectral profile. The substitution of alternative XFORM mappings demonstrates the modularity and generality of the process diagram. These mappings also demonstrate the creative and generative potential of cymatic synthesis.