The A-117 has a combination of a digital noise generator and an 808 source.
The digital noise generator uses random sequences of square waves, (18-band slewed shift register), whose rate can go from random clicks to pure noise.
The colour of the noise is very different from the analogue noise produced by the A-118. In addition to a manual setting, the rate can be controlled by an external clock (such as a VCO, LFO or MIDI clock).
The 808 Source recreates the multi oscillator array that was used in the Roland TR808 drum machine as the basis of the sound of the hi-hats, cymbals and cowbell.
The cowbell uses two oscillators and the cymbal uses six
