Most filters can emphasize the frequencies just before those that are reduced in volume. Resonance is the degree of emphasis that occurs. It makes the filter much more audible and gives it character - it would otherwise sound like just altering the equalisation - and is the foundation of the acid sound....
Electrocomp 200
The Electrocomp 200 is a 2-VCO monophonic synthesizer expander module. It did not
come with a keyboard but as an expansion module for the 100 or the 101, which
included a keyboard. The Electrocomp 200 features two VCOs, which have outputs for
sine, triangle, and pulse waveforms, and a noise source. There is a spring reverb, a
low-pass VCF, a high-pass VCF, an ADS envelope generator, a ring modulator, a mic
preamp, and a dual 3-channel stereo mixer.
The eml-200 came in 2 colors, blue and silver. The later ones were silver and the
original ones were blue. The blue 200s were also built into larger cases and were a bit
heavier than the more recent silver ones.