This patch actually has no filters or EQ. Instead, it had EIGHT oscillators per voice, each with harmonics only over a given octave. (Each oscillator is playing the same pitch.) The eight MIDI general purpose controllers are used to adjust the volume of each of the eight. Unlike normal filters, which have some kind of slope on each side of their center frequency, this method gives you the effect of infinite cutoff at an exact frequency.

Note the sound is recorded directly from Moselle: no hardware or external processing was used.

Devs, Prods & Tags: Moselle SynthesizersMoselle