Modal VST is a percussion synthesizer that models 2d square membranes and 1d linear resonators such as strings. Up to 256 partials are rendered using a bank of harmonic oscillators. Modal VST is bundled with Radian VST, which uses the same technique to model circular membranes.
Due to the ability to stretch the partials, Modal is able to produce timbres similar to thick bass guitar strings and can be applied to other acoustic emulations.
The demo version is limited by an intermittent noise. The licensed version is bundled with three other percussion synthesizers.
Price: $20 including Radian synth.