kx77free has released a fairly comprehensive VST synth that uses a combination of subtractive and additive synthesis. The features list contains some useful features, like plenty of envelopes and LFO's, 2x filters and the like.
Full parameters controls to make Additive Waveforms with no aliasing.
Full 32 bit High Quality Waveforms.
Same quality for all clock frequencies: 44.1 khz to 192 khz.
independent WaveTracer engine: KxWaveTracer.exe.
All modulations are pre-connected, no cables on the GUI.
3 Polyphonic EGs with for each segment: curves, velocity and Kbd controls.
1 Monophonic EG with for each segment: curves, velocity and Kbd controls.
Multiple trigger sources and sync for the EGs and the LFOs.
2 Oscillators with 2 waveforms and 2 outputs with Phase modulation and Sync.
2 independent Sub Oscillators.
2 Monophonic LFOs with 2 Rates and ASR EG.
2 Mulitmode VCFs.
Mixer with 6 sources: Noise, Vco1 1-2, Vco 2 1-2, Ring, Vco1 Width, Vco2 Width and 3 outputs: VCF1, VCF2, VCA.
Each mixer voice can be modulated by different sources.
Noise Generator with an EQ.
6 host sync clocks.
2 Midi inputs.
2 Delays with sync, multimode filter and modulation oscillator with sync.
Full NRPN implementation: More 500 parameters.