Just FYI editing the spectra is usually referred to spectral or additive sysnthesis.
Wavetable synthesis involves a table of single-cycle waveforms that you then sweep through, either manually or preferably with some sort of modulation source. The PPG Wave is the most famous case, and Ensoniq's Transwave technology was basically the same thing. Typically you'll start with 2 waves of completely different harmonic spectra and interpolate between them. IIRC there's a quite affordable PPG wave for iPad now from Wolfgang Palm (who is the authority on this method of synthesis).
I was forgetting for a moment the key part of wavetable was the sweep/interpolation. Silly me! The name of the Wolfgang Palm App is the Wavegenerator I mentioned above -- been playing with it a while, v. v. cool, but (as per your original comment) I can't stray to far from presets without sounding horribly metallic.
Wavetable synthesis involves a table of single-cycle waveforms that you then sweep through, either manually or preferably with some sort of modulation source. The PPG Wave is the most famous case, and Ensoniq's Transwave technology was basically the same thing. Typically you'll start with 2 waves of completely different harmonic spectra and interpolate between them. IIRC there's a quite affordable PPG wave for iPad now from Wolfgang Palm (who is the authority on this method of synthesis).