IVOR is a free software synthesizer that allows you to compose and perform microtonal music. It has just seen a major update to version 2, making it more versatile and powerful than ever. It is a virtual analog synth that includes frequency modulation, ring modulation, pulse-width modulation, saturation, filters and various features specific to microtonal and spectral music.
The biggest change is the MOD-GEN section which allows deep control of various synth parameters with envelope generators, LFOs and AROs (audio rate oscillators).
Those AROs are especially important, as they allow the introduction of additional sideband spectra to the signal which give a more dense forestry of partials to your sound. This right here is a key aspect of designing sounds in IVOR2. There are several of these AROs at various parts of the signal chain for you to experiment with.
The AROs can be tuned to microtuning-related intervals. This introduces tuning-related sidebands into the signal. There are over 100 partial sets to choose from, and you can load up your own via text file import. This is especially powerful for the creation of inharmonic or quasi-harmonic timbres that are matched to inharmonic or quasi-harmonic tunings, in such a way that sensory dissonance (timbral dissonance) can be reduced for extremely exotic scales.
Or you can just keep it to the harmonic series and play 12-tet music like a traditional synth. It’s good at that too.
But let’s stick with microtonality for a moment. You can tune IVOR2 to whatever tuning system you want. Equal tempered and just intonation tunings are possible, as are non-octave and stretched-octave scales. Totally arbitrary, irregular, historical and traditional scales are all possible too. There are no limits here, and you will be rewarded greatly for stepping outside of your comfort zone.
IVOR2 is very light on the CPU, just like its predecessor. I can run a whole bunch of instances of IVOR2 in real-time with my 3 year old laptop.
It is a quirky synth with its own characteristic sound. Yes it can do a lot of classic sounds too, but its unique aspects make it capable of so much more.
Make sure you read the manual and play through all the factory presets (I designed a bunch of them myself) so that you can get a sense of what is possible with IVOR2.