Hello Antoine,
indeed -.01 does not work. With -trans you can give either constants (as numbers) or filenames that are supposed to contain time varying
transposition. The filename variant is selected if the neither of the first two characters is a number. You can add the leading zero for the bc output as follows
transp=-0.01;
while [ $(echo “$transp>=-0.03” | bc -l) -ne 0 ] ; do
supervp…
transp=$(echo “$transp - 0.01” | bc -l | sed ‘s/^-./-0./’);
echo “$transp”;
done
Best
Axel
Hello Axel,
It is working for me now so I was able to try several things. However I am surprised by the results:
Regards,
Antoine Escudier
Hi Antoine,
https://ccrma.stanford.edu/~jos/pasp/Time_Varying_Delay_Effects.html
The central point is that delays create a comb filter effect. The difference between delay lines and transposition is the fact that with transposition the different sinusoids are displaced and can therefore not cancel each other completely, moreover the frequency displacement will increase with the frequency of the sinusoids and the phase displacement is time varying differently for different frequencies - all this leads to the fact that the regular structure of the comb filter effect cannot be created with the standard AS transposition.
You can get the effect you need in AS very easily by means of doing transposition (without envelope preservation) when you deactivate the time compensation in the transposition dialog. Deactivating this compensation produces the historical effect of playing tapes faster or slower) and is therefore exactly what you need. You can then modify the transposition over time by means of the bpf editor. I never tried this but you should be able to generate the flanging effect without problems. For chorusing you would simply superimpose more than two transformed signals using different transposition functions.
As a little note I’d like to mention that transposition of an 100Hz sinusoids using 0.01 cents produces a frequency difference of 0.000577Hz. that means the
period of the beating would be nearly 30min, for another partial at 100Hz t period would become 3min.
The term pitch shifting is unfortunate because misleading. I don’t think we use it in AS. We have named the transformation “transposition” and this transposition preserves frequency rations between all sinusoids. On the other hand we have as well a frequency shifting operation (similar to what may elsewhere be called ring modulation) you find thus effect in the same transformation menu of AS. This effect shifts the spectrum and therefore it creates inharmonicity.
I will be on holiday in july, but certainly read my mail regularly and will try to respond.
Hi Antoine,
https://ccrma.stanford.edu/~jos/pasp/Time_Varying_Delay_Effects.html
The central point is that delays create a comb filter effect. The difference between delay lines and transposition is the fact that with transposition the different sinusoids are displaced and can therefore not cancel each other completely, moreover the frequency displacement will increase with the frequency of the sinusoids and the phase displacement is time varying differently for different frequencies - all this leads to the fact that the regular structure of the comb filter effect cannot be created with the standard AS transposition.
You can get the effect you need in AS very easily by means of doing transposition (without envelope preservation) when you deactivate the time compensation in the transposition dialog. Deactivating this compensation produces the historical effect of playing tapes faster or slower) and is therefore exactly what you need. You can then modify the transposition over time by means of the bpf editor. I never tried this but you should be able to generate the flanging effect without problems. For chorusing you would simply superimpose more than two transformed signals using different transposition functions.
As a little note I’d like to mention that transposition of an 100Hz sinusoids using 0.01 cents produces a frequency difference of 0.000577Hz. that means the
period of the beating would be nearly 30min, for another partial at 100Hz t period would become 3min.
The term pitch shifting is unfortunate because misleading. I don’t think we use it in AS. We have named the transformation “transposition” and this transposition preserves frequency rations between all sinusoids. On the other hand we have as well a frequency shifting operation (similar to what may elsewhere be called ring modulation) you find thus effect in the same transformation menu of AS. This effect shifts the spectrum and therefore it creates inharmonicity.
I will be on holiday in july, but certainly read my mail regularly and will try to respond.
Best
Axel
Hello Axel,
Thank you very much for the Julius O.Smith’s online book!
Thank you also for explaining that it makes no sense to transpose by 0.01 but since I do not know how to go from Hz to Cents and how to infer the period of beating, I just try anything as many other musicians probably do…Is there somewhere a summary of useful simple calculations that I could do without asking you?
2)
I apologize I did mean frequency shifting when I used the term pitch shifting
Thank you a thousand times for taking the time of answering me.
Best regards,
Antoine Escudier
Hi Antoine,
the cents measure is specifying a ratio in terms of half tone steps times 100.
The formular to go from cents to ratios is
rat = 2^(cents/1200)
so for 1200 cents you find
rat = 2^(1200/1200) = 2^1 = 2
that means 1200 cents == 1 octave.
Now to get the beating. Beating is due to overlapping sinusoids cancel or enforce each other due to changes in phase relations. If you observe this in AS then the critical factor is the window size. The smaller the window the larger is the distance of two sinusoids that create beating.
The period of a phase relation cycle for two sinusoids is given by the frequency distance. So if you start with a sinusoid with F=100Hz
transpose by 100cent and listen to the original mixed with the transposed then frequency difference will be about 6Hz and so the beating frequency will be this frequency.
Whether you hear two sinusoids beating or does obviously not depend on the windowsize you use to analyze the sounds in AS. It depends on the sound perception in the ear. As you may know you can express two sinusoids equivalently as 1 amplitude modulated sinusoid or two stationary sinusoids. Which are the frequency ranges that lead to the perception of beating is a psycho acoustical question that is outside of my scope. I am pretty certain that for frequency difference above 50Hz you don’t hear beating but two sinusoids, and on the other end below 12Hz you will hear beating (amplitude tremolo). I am not sure about which processes in the ear create these limits. May be the critical bands are involved?
Best
Axel