This instrument gives you full control over playback speed and playback position in realtime, play forward, backward, in nonlinear fashion or just freeze the sound. Works nicely for very slowly evolving drones and soundscapes when using extreme playback speeds, like 0.5% of the original. Rekombinator II has two waveform slots, so you can blend two samples. Each slot has independent control of basic engine parameters, like speed or playback position and separate audio path. Then there's hybrid modulator, introduced in Sawmill, where you can use step sequencer controller to render an LFO waveform. You can use it, for example, to create a nonlinear playback curve, make the playback head position travel around the waveform in fancy ways. Like in first Rekombinator, it is possible and not complicated to use any samples.
The instrument requires full version of Kontakt 5.8.1 (Kontakt 5 with latest update) or Kontakt 6. When pushed, it can produce noticeable CPU load, it's fine on my 10 years old 6 core, so I think any half decent modern processor should handle it easily.
Rekombinator II is now retired and replaced by Rekombinator III.