Aikido by Bastl Instruments is a four-VCA mixer with some special features. In the main, the module features four VCAs with volume fader, bipolar CV attenuator and click-free mute button. Since the CV inputs and signal outputs are normalized, the module also makes a good figure as a four-channel mixer with CV control, provided that only output D is patched. Thanks to bipolar CV attenuators a closing instead of opening of the respective VCA can be generated depending on the control voltage. Up to this point Aikido has some similarities with many VCAs.
What makes the module stand out from the crowd are the side chain input, envelope follower and spectral follower. The envelope follower extracts a control voltage from the audio signal of the mix output which is always oriented to the level. The ENV-CV output is normalized to CV A, this way sidechain compression is achieved. Alternatively, another signal like a kick drum or snare from another signal source can be used to achieve this effect. The Spectral Follower works similar to an envelope follower, but it gets its "information" from the bass, mid or treble of the normalized channel D respectively the mix output. With Aikido you get much more than just a quad VCA mixer, because the internal possibilities for obtaining control voltage together with pre-wired signal paths are a guarantee for very lively level responses.