inSIDious has been developed over 5 years by Mike Clarke, a veteran video game musician and programmer, who spent his formative years playing Commodore 64 games and listening to their music. It was this music that set him on his career path, giving him huge respect for and admiration of the SID chip and the sounds that it could produce.
After using SID sounds in many productions over the years, Mike felt that none of the existing VST emulation attempts were anywhere near suitable as a replacement for his HardSID Quattro sound card (containing 4 actual SID chips). So, he took it upon himself to create his own emulation to be as close as possible to the real thing.
As a result, inSIDious is unlike the many 'SID-like' VSTs in existence, which have the basic waveforms and little else. Instead, it is a re-implementation of every feature of the chip as accurately as possible; this includes even 'bugs' and quirks which help give the chip its iconic sound!
The SID chip (and by extension inSIDious) has three independent digital oscillators that generate 4 fundamental waveforms: Pulse, Sawtooth, Triangle, and Noise. The Pulse waveform's width can be set to any one of 4096 positions representing the complete range from pure square to a pulse thin enough to be silent.
The Noise waveform is a digital pseudo-random noise generator that can be pitched up and down and sounds characteristically "8-bit". Together with inSIDious innovative "SFX" button, this can be an amazing tool for creating classic sound effects.
The Pulse, Sawtooth, and Triangle waves can be enabled in any combination, giving rise to a unique set of extra waveforms. Also, any oscillator can be synchronized to the frequency of another to produce a "Hard Sync" effect.
When an oscillator is set to the Triangle waveform (or Tri+Pulse), it can use another oscillator as a carrier frequency to produce ring modulation, which can produce bell-like metallic sounds and effects.
Each oscillator has its own envelope generator, which allows an ADSR envelope to be applied to the volume, as well as a PWM envelope and LFO, and a pitch envelope and LFO, all with independent timing and sync values.
The filter is an analog, multimode resonant filter that can be set to low-pass, band-pass, high-pass, or any combination of the three. The 6580 version includes six curve models as well. For modulation, an envelope and LFO are included. By running Reaktor in FX mode, external audio can be run through this filter!