Seer Systems Reality
Seer Systems has created a very extensive and full featured Analog Synthesizer Software Emulator program for the Windows 95 or higher platform. Complete control of oscillators, LFO, filters and four envelopes. Memory is limited only by the size of your hard disk. It even has multi effects like reverbs for sprucing up your patches. A bit pricey for a software synth and the lack of any Mac version limits this software to only a few serious users. However once you master it you can sell that old ARP 2600 and Matrix 12 because Reality can muster fat analog synth tones just as well! Unfortunately Seer Systems doesn't seem to know that there is another computer system out there - the MacOS. Reality is currently only available for Windows 95 / Pentium II or higher.
Demos & Media
Images from Seer Systems web site.