Rubberduck is a virtual acid and techno software-synthesizer for your pc.
Its whole concept is based and created on the legendary cult synthesizer the Roland TB-303.

With this bass synthesizer released for Windows 95 in 1996 (way before Propellerheads Rebirth, was available), d-lusion pioneered the market of realtime software synthesizers on standard processors. Roughly based on the the well known TB-303, Rubberduck's synthesis model consists of an oscillator wave with a resonant filter sweep applied to it combined with an efficient hardware sequencer design which resolves in the typical twisted, screaming, bubbling bass sound that is often used in Acid House, Goa Trance, or Techno productions.

Rubberduck featured realtime digital resonant dynamic filters, frequency and volume envelope (DCA, DCF), 4 basic waveforms, dual oscillator sound generation (starting with version 2.0), a 224 note sequencer, a drum section where samples could be synchroneous played back, an effect unit (delay / feedback / distortion) and was fully Windows 95 compatible.

Here are some key features of "Rubberduck RD H30+":
· Standalone software synthesizer
· 5 standard oscillators
· Dual oscillator model including "morphing"
· Realtime resonant filters
· Great user interface & skin support
· Frequency and volume envelopes
· 256 notes step sequencer
· Sound effects: hall, reverb, distortion
· 16bit 44.1 khz CD quality
· Midi support
· .wav rendering option.wav rendering option
· Groove section for drumloops