MOTM

I would partly agree.  If you examine plots of the sound of one 
instrument at varying pitches and amplitudes you will very quickly 
get the idea that there is a lot more going on than you can see in 
the plots, because they vary so much.  This is why additive 
synthesis in itself doesn't yield too much in the way of interesting 
sounds.  However it is a good starting point for gaining an 
understanding of how to synthesize a traditional instrument.  And it 
can be combined with things like modulation and filtering to bring 
it to life.  I'm just interested in using it as a tool to gain 
insight into what is happening in a particular sound.  It would be 
equally interesting if an analysis tool could easily show you the 
frequency response of an instrument body, if it could be done 
without sticking transducers all over the place and then applying a 
variety of excitation sources.
BTW I've downloaded a trial version of a program called SpectraPLUS 
for the pc from soundtechnology.com.  I have emailed them since I 
can't find anywhere what the cost of a fully licensed version is and 
I can't get through on the phone.  It looks fairly capable, but I 
bet I can't afford it.