The Viking is a free software synthesizer available as a standalone application. It is portable, requiring no installation. Simply unzip the .zip file and run the executable inside.
The Viking uses additive synthesis to produce Dynamic Tonality tunings and timbres. Scale pitches result from successive additions and subtractions of a period (e.g., an octave) and a generator (e.g., a perfect fifth). The period and generator can be set to any size, making a wide variety of microtonal tunings easily accessible.
The new version (2.0) has been rebuilt from scratch for efficiency, cross-platform capability, and new functionality. Not only does it now allow full manual control of partial amplitudes, it also features a new morphing capability that allows you to create two different amplitude configurations, and morph between them using any combination of a slider, envelope, and LFO modulation.