The EKS-9 is a special-purpose VST / AU software synthesizer, designed to recreate the sound of analog electronic kickdrum sounds - hence the name EKS (Electronic Kickdrum Synthesizer).
The plugin offers two modes, 808 and 909, each with their own, characteristic sound. It goes far beyond the capabilities of vintage analog hardware, however, and introduces new parameters, most importantly it offers precise control of the pitch. Additionally, despite the fundamentally different models employed, all parameters apply equally to both the 808 and 909 mode.
The user interface is organized into four sections controlling the pitch, the amplitude and pitch envelopes, the attack stage and finally pitch modulation. This layout makes it simple and straightforward to program your own patches or modify existing ones.
The included PDF manual provides detailed information about every parameter.