>>>>> "TK" == Tobias Kunze  writes:

 TK>  | To create an acceptable morph you have to be able to
 TK>  | isolate these factors and control them individually. This
 TK>  | is moderately easy for monophonic sounds but spectacularly
 TK>  | difficult for polyphonic sounds.

 TK> Problem is, that `morphing', as Jean Piche pointed out, is
 TK> not a technical term.  In fact, it wouldn't really denote
 TK> anything at all, wouldn't its ethymology suggest some sort
 TK> of treatment of something's `morphology'.  In other words,
 TK> the concept is intuitive, but its realization is not.

One interpretation is that morphing is the process to go from one
"state" to another "state" in a continous way. If the states are
represented by sound, then would morhping be the process to reshape
the first sound into the other in a contious way.

If you morphy between two even key sounds you may do with simple
crossfading. However, if you take two sounds of diffrent key and morph
them, then you would along with the frequency component changes also
have a changing frequency so that along with the character change you
would also have a slide upwards or downwards in frequency. If you add
such stuff as vibrato to the sounds (diffrent vibrato) you will have
to allow the vibrato to change along everything else. These kind of
morphing effects have a certainly an place in the sound picture, but
advanced DSP technologies can have a pretty hard time to preform them
in a good way for a pair of given signals.

In order to create a good sound morph I'd say that you better modify
the sound sources properly instead. Changing just pitch, vibrato and
the mixing between them can be quite enougth for some purposes.

 TK> Surely, for some processing to be called a true `morph',
 TK> you'd have to have a handle on every psychoacoustically
 TK> important feature of the signal.  But you won't be able to
 TK> get that from any known DSP technique.  Even more, if you
 TK> look close enough, `morphing' doesn't even work in graphics.
 TK> Typically, you'll see two images "approach" each other
 TK> through a more or less boring, brownish and blurry swamp of
 TK> intermediary states.

One must transform the set of poles and zeros (and their movements) in
the original signal into the set of poles and zeroes (and their
movements) in a interpolation way, selecting which poles/zeros which should
be interpolated between each other is a compulational problem of it's
own except for the computational problem of finding them
out. Obviously is this attack on the problem not so effective but it
will do it properly.

 TK> The general problem here is that the salient features you
 TK> think you're interpolating in the straightest manner
 TK> imaginable, will inevitably engage in unforeseeable complex,
 TK> interesting and distracting interactions (to counteract the
 TK> noisy intermediary states, composers have always spent the
 TK> extra effort of actually inventing and carefully shaping
 TK> each state--as opposed to applying a mechanism).

 TK> I think one can not meaningfully combine `morphing' and
 TK> `signal processing' in any single sentence.  Except in the
 TK> preceding one, of course ;)

They are not easilly married, rigth :)

Cheers,
Magnus