The Quilcom Subtractor is a free VST synthesizer instrument which is the result of experimentation with the idea of making a synth using only noise as a source.
The Quilcom Transformer is another take on additive synthesis. There are 6 identical generators. At the top is a bar graph where you set the relative value of 24 partials. The resulting single-cycle waveform is shown lower left in the generator. To clear the bar graph, just double right-click. Graphs can be saved or loaded for use in other generators and presets.
The Quilcom QX7 is a free VST synthesizer instrument inspired by the amazingly successful Yamaha DX7, first made available in 1983.
The Quilcom Q-50 is a free VST synthesiser instrument inspired by the Roland D-50. It’s not an emulation and the presets and embedded wave files are not a copy of the originals. However the architecture is very similar.
The Quilcom Multiplier 2 is a free quadruple chorus and pitch-shift vst effects unit. The 4 stereo effects blocks are identical. Each block provides an optional input state variable static filter with adjustable cut-off frequency and resonance. This is followed by an optional chromatic pitch shifter that allows you to select musical intervals for the pitch-shift (with a fine tune setting).
Quilcom 4EA+ is a free VSTi synthesizer which used both additive and FM techniques. It comes with 65 presets included. They cover a wide range of types and hopefully many of them can be easily adapted to edit towards what you may have in mind.