This clip shows you how to make a completely analog wavetable synthesizer:
The basic idea is quite simple. If you plug two analog waveforms into a mixer, you can morph between the two waveforms (and sounds) by applying different mix levels to each source. If your mixer has an inverter, you can also subtract one waveforms from another.
If you add a VCA to the mix (pun not avoided) then you can modulate the different mix levels using an LFO or envelop, and have your sound evolve gradually.
All of this applies both to simple and complex waveforms.
Finally, if you want gradually to morph across multiple waveforms, a module like Doepfer's A-144, connected to a VCA comes in really handy for morphing through up to four waveforms.
Gear used (not abused) in this video: Moog Mother 32, Voicas 248 VCA and Mixvert8r, Doepfer A-144, Maths, Z-3000.