Straightliner

"Straightliner is a straight-lined subtractive synthesizer in a modern guise. You will find the well known building blocks of classic analog synthesizers (4 oscillators, a filter, 2 envelope generators) patched together in the traditional way. Now you are probably tempted to say ’boring!’ - however, the building blocks themselves offer much more flexibility than commonly seen in subtractive (aka ’virtual analog’) synthesizers: Instead of relying on a set of fixed waveforms, Straightliner’s oscillators support loading of arbitrary (single cycle) audio files which may be even stereo. In turn, the whole signal path is laid out in stereo. The standard ADSR model for envelopes is replaced by a flexible modulation generator which allows to define an arbitrary number of breakpoints. The heart of subtractive synthesizers is the filter, of course. In this department, Straightliner offers a multimode filter with various modes, among them the usual suspects like lowpass, highpass, bandpass, but also bell- and shelving types and some ’morphable’ types and (remark: at this early beta-stage, only the ’Moogish Lowpass’ type is implemented)."

You can find it as a free download in the Products section of Robin Schmidt's Music Engineering Tools. Be sure to check out the rest as well. via Sonic State.