I love my Synthesis Technology E350 Morphing Terrarium Voltage Controlled Oscillator. I need me my complex waveforms. With an expander module, you can enable what's called "phase mode," and that makes for a nifty oscilloscope display if you draw Lissajous figures. (Look it up.)
In order to keep things moving, so to speak, I used a little dual low-frequency oscillator to slowly modulate a Doepfer A-125 Phase Shifter's output of the XY Out of the E350, and ran the Z Out into another SynthTech module, an E440 LP filter. I also twiddled knobs all over the place.
I noticed a couple things, if I cranked up the resonance on either the filter or the VC phase shifter, the patterns would change quickly and dramatically as the controls swept through prominent harmonics.
An oscilloscope is mandatory gear in a studio or at a gig because synthesis, IMHO, is also a visual experience.