Hello everyone, 

I just joined the list in order to find help in making a wavetable synth. This 
synth would do both morphing and frequency wavetables. Morphing is a way to 
play different waveforms over time and so to get an additional sound dimension. 
Frequency wavetables are used to avoid aliasing by filtering harmonics the 
higher the frequency go. I started with the frequency wavetables and then I 
will do the morphing between different waveforms. 

As an intern at Rebel Technology, I started making wavetables patches from 
earlevel articles. In those patches, common waveforms are generated inside the 
code (tri, square, saw). Now I want to generate some more complex waveforms 
from an editor called WaveEdit (free). They come as 256 samples single cycle 
.wav files. Then I change them into static data in a header file. Once I have 
this, I can start with frequency wavetables. The key point of frequency 
wavetables is the filtering. I have to filter enough harmonics so the aliased 
frequencies do not come back under 18KHz (audiable range). But I must not 
filter too much if I don't want to get gain loss. 

At the moment I managed to make a 3550 taps FIR to filter every octave 
wavetables. Unfortunately, with complex harmonic rich waveforms, I still have 
audiable aliasing from 2kHz and gain/amplitude difference when wavetables 
cross. 
So now I am wondering: 
About aliasing, should I cascade two FIR instead of increasing the taps? 
That could be a solution if the stop band is not attenuated enough. According 
to octave fir1, stop band attenuation is 50dB to 70dB. 
About gain loss, will "harmonic rich signal" always sound lower when filtered 
even if gain is the same? 
I haven't normalize wavetables yet. I might have my answer afterwards. 

You can have a look at the patch code but you won't be able to try it if you 
don't get Rebel Technology Owl files. 
https://github.com/alexniger/OLWpatches-RebelTech/blob/master/WTExtWavePatch.hpp
 
All other links are in the readme. 

Best, 

Alex 


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