Brady Boettcher has released gRainbow, a free pitch-detecting granular synthesizer plugin for Win, Mac & Linux. The plugin is available for download at bboettcher3.github.io/grainbow and there is no expiry date for this offer. 
gRainbow is the open-source, cross-platform synthesizer you’ve been looking for! With pitch detection, granular synthesis, and sampling capabilities, gRainbow is the perfect tool to take your sound to the next level.
So why choose gRainbow? Traditional granular synths have a few shortcomings – they can produce inharmonic tones, manual pitch matching is often required, and pitch shifting can create unwanted artifacts. gRainbow solves these problems by allowing you to use longer, pitch-diverse audio clips, automatically producing harmonics matched for MIDI input, and avoiding too much timestretching by generating harmonics that are already near their target pitch.
Let’s get into the nitty gritty. Notes are one of 12 notes in the chromatic scale, and gRainbow repeats its single octave over all MIDI notes. Generators create grains for a particular note at a particular position in the audio clip, and candidates are a collection of viable positions in the audio clip where the pitch is harmonic with a particular note. Parameters are just like usual ones, but organized a bit differently.
When an audio file is loaded into gRainbow, a pitch detection analysis is ran to segment the clip into discrete pitches over time. Next, gRainbow finds up to 6 pitch-matched position candidates for each note, guaranteeing harmonically agreeable grains. Finally, the user customizes each note and its generators (i.e. changing parameters and candidates) to their liking, and can save everything into a preset to avoid processing things again next time.
