The Skew Fade LFO is a 3hp analog Low Frequency Oscillator with a wide range of cycle rate and waveform. The three rate settings switch from 3.5 minutes per cycle to 20hz, which is audio rate.
Triangle waves can be skewed from sawtooth waves to ramps, and square waves' pulse width can be modulated. These adjustments can be voltage-controlled.
Bicolor LEDs indicated positive voltage with red, and negative voltage with blue.
Here's a demo from the manufacturer showcasing the various waveforms: