[sdiy] moog high pass flter

[Ian Fritz]

At 09:30 PM 12/8/2002, harrybissell wrote:

>I'm referring to the normal "synth" use of a VCF... ie filter sweeps for
>timbre modification.

I agree that HP timbre sweeps are generally weaker-sounding than LP timbre 
sweeps.  But I don't agree that this is the "normal" use of a 
filter.  Setting the base timbre of a sound using filters is just as 
important, at least to me.

>A 24dB/oct HPF might be a little extreme for knocking the lower harmonics out
>of a clarinet waveform.

Yes, a lower slope is more appropriate for acoustic emulation.  Remember, 
though, that even if you totally knock out the fundamental, your ear/brain 
reconstructs it. (Perhaps this is why HP timbre modulation is perceived as 
relatively weak).  I've never tried a 24dB/oct HP, but it sounds like fun.

My double-pulse and Wavolver waveshapers include a control to subtract the 
input waveform from the output, which provides a very interesting 
HP-filter-type of effect.  Do listen to the demos.  :-)

>A pulse wave can have more higher harmonics than fundamental as well....

Are you sure?  I think the fundamental is always stronger than any 
harmonic.  This is easy to prove with trig identities for the first couple 
of overtones, but I don't have a general derivation.  Perhaps you would 
like to give us an example.  Name your duty cycle!  :-)

   Ian