BOLT makes use of a Harmonics Synthesis engine that provides a rich sound, one that doesn't necessarily need filtering to achieve a tone hefty in character.
The synth itself provides multiple oscillators that you can easily tweak from simple sine waves to rich timbres replete with overtones, all with the twist of a knob. It works as a VST or AU plug-in within your DAW. Available for download, Nektar Technology's BOLT is a software synthesizer for use in composition and sound-design endeavors.