Rainbow is a versatile PC synthesizer offering standalone and VST 2.0 plugin compatibility. Create music with ease using its user-friendly interface and powerful sound-sculpting capabilities.

What really impressed me was the level of control I had over each oscillator. There's a handy waveshaping distortion knob that adds some real grit and character to the sound. Plus, the Coarse/Fine tuning knob makes it easy to get things just right. Additionally, users can select different LFO modes and keyboard tracking modes for even more variability.
In terms of envelope control, there's an APDSR (Attack/Peak/Decay/Sustain/Release) level envelope for each oscillator. This is great for shaping the attack and release characteristics of each sound. I also had a lot of fun playing around with the 4x4 frequency and amplitude modulation matrices for creating complex feedback settings.
Of course, no synth would be complete without a good filter section. This one offers LowPass, BandPass, or HiPass filters, all with their own cutoff APDSR envelope, envelope modulator, and resonance knobs. Additionally, there's a clever 'Double' mode that stacks two filters in series for even more tonal shaping possibilities.
The synth is fully MIDI automatable, which is great for live performances or for use in a DAW. There's even a 16-step sequencer/arpeggiator that comes in handy for creating complex patterns. And for the finishing touch, there's a high-quality oversampling mode with anti-aliasing filter that ensures your sound will sound great in any situation.
Overall, I was really impressed with this software synthesizer. It's user-friendly, incredibly versatile, and sounds amazing. If you're in the market for a new virtual instrument, I highly recommend giving this one a try.
Version 2.5: N/A