http://www.native-instruments.com/en/community/reaktor-user-library/entry/show/8572/
This ensemble is a near-perfect emulation of the extraordinary Commodore 64 sound chip. Included are all features of the original hardware:
* Three channels with Triangle, Square/PWM, Sawtooth, Noise and combined oscillators.
* Ring modulation and hard sync.
* The classic SID saturating filter that is incredibly important but missing on most emulations.
* LFOs and envelopes for pulse width, pitch, amplitude and filter cutoff.
* Step table at up to 50Hz for that genuine sound.