The A-101-1 is a Multitype input filter, i.e. we have separate LP, BP and HP inputs and a common output. The inputs are normalised so we can use the LP input and three potentiometers to mix the type of filter we want.
More details can be found at Doepfer’s homepage:
We use three mixed A-110 VCOs as input, controlled by an A-155 Sequencer. The filter is controlled by the VCO CV from the sequencer, an A-140 ADSR and a LFO (very slow triangle wave). There are two outputs on the A-101-1, the second one decreases volume when filter emphasis (resonance) gehts higher. That’s the one I use here. I start with only LP input, blend over to BP and then HP. Resonance is increased manually and we can hear the rather sudden and quite intense resonance of this filter – this is quite useful for special effects, bassdrums, etc. Later on, I increase the LFO frequency up to audio (around 4-5 kHz): since the filter uses vactrols, it will not follow too high modulation frequencies (no audio filter fm).
Here we go:
Quite an interesting filter! Very creamy and bold sound characteristics, but resonance will come quite screaming and suddenly. The three inputs can be used by different audio sources and may offer very special sound capabilities not found elsewhere.