well i think the simplest would just be plain addition: you find the waves on the longest timescale you're considering, then add to that the waves on the smaller timescales (i.e. the waves along the wave, etc.)
that shouldn't be too hard to do: e.g. start with the raw data, approximate waves for the longest timescale, subtract that out, and then repeat for what you have left, decreasing timescales along the way.
not sure about "additive synthesis". sounds like perhaps the procedure above in reverse? (start with waves on various timescales and add 'em up?)
