One of two "synth on a chip" integrated circuits produced by Curtis Electromusic in the late 1980s. The 3394 contained everything needed for a basic voice circuit: a VCO with triangle, sawtooth, and pulse, a four-pole lowpass VCF, and a VCA. Because the 3394 was intended to be interfaced with a microprocessor system, the VCO was not precisely calibrated or linearized; it was assumed that the synth's auto tune routine would take care of setting the scaling for each VCO in the system. However, the VCOs were internally temperature compensated with a built-in tempco.