wave scriber [was: Modern analogue ...]

[mbartkow at ET.PUT.Poznan.PL]

Dear Paul and all diy'ers,

>   I still intend to make my wave scriber, 32 sliders which you draw 
> the waveform on, each been able to modulated from one 3 modulation 
> busses by varying amounts and each also haveing a seperate insert 
> aswell... ok, Im mad, it could be done with a dsp with 
> polyphonic/filters/vca/ringmod/etc/etc, but wheres the fun? wheres the 
> chip that smokes, the thrill of getting a noise from it?

It has been pointed out already, that drawing the wave shape with sliders
is not neccessarily the most efficient way of utilising many controllers
to create new sounds. Let's assume one has 32 sliders (or 32 voltage 
controlled slots) which are aimed at creating possible wide range of timbres
as their positions/values change. Additive synthesis seems the better way
to go, since moving one slider changes the timbre more dramatically than
it is achieved with sliders controlling the wave shape at 1/32th point of 
its cycle. 

However, I think that using sine partials in additive synthesis
is boring, since each partial alone sounds the same, and only in the global
context they have some impact on the timbre. Walsh functions are slightly
better in terms of timbral variety of each individual "sequence" (the
Walsh equivalent of "frequency"), although still many of them sound similar.

The optimal solution seems to be a set of waves whereby each exhibits a unique 
timbral character, yet it is possible to obtain any spectrum by mixing them 
in various proportions. The latter requirement means, they should constitute 
a complete basis, possibly an orthogonal one (as in case of Fourier's sine basis). 
Note that Bob Moog concluded this very early and introduced a basis reduced
to few waveforms, namely sine, square, saw and triangle. These waves are not 
orthogonal, yet each of them is quite unique in timbre. Moreover, their impact
on the timbre of final mixture is independent from each other ant therefore
they could be called "perceptually orthogonal" as oposed to mathematical ortho-
gonality.

There are many sets of orthogonal functions which could be used in extended
additive synthesis. For example, Chebyshev polynomials or the orthogonal basis
introduced by Legendre. In my opinion, the best set of 32 wave shapes is still
to be determined empirically.

regards,

m.b.

--

Maciej Bartkowiak
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