Nord's classical Virtual Analog Synth Nord LEAD 1/2/2x/3/4/A1 and Nord Rack versions

Re: Lead A1 Pulse Wave Out Of Tune

Postby Mr_-G- » 20 Jul 2022, 00:19

You seem to be using an extreme pulse (not a truly square wave). I can reproduce it in the NS2 with the initialised synth.
Try changing the shape parameter which controls the pulse width so it becomes closer to a square wave (in my setup the shape parameter set anywhere from 1.0 to 5.0 works), it does not sound out of tune any more! :geek:
There is a similar effect called Schroeder's auditory paradox where a special waveform sounds out of tune because the ear hooks into the 'wrong' (closest) harmonic (rather than the fundamental) when playing certain intervals. In this case I am not sure if this is the same situation (a perceptual effect) or the extreme pulse shape actually loses, to some degree, the fundamental frequency.
You can check this by computing the power spectrum of the sound and see what happens one octave apart.
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Re: Lead A1 Pulse Wave Out Of Tune


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Re: Lead A1 Pulse Wave Out Of Tune

Postby DJKeys » 20 Jul 2022, 01:18

I think if you close down the filter so you hear just the fundamental, I think you will agree the note itself is not out of tune. The harmonics in the sound are playing tricks on your ears I believe-

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Last edited by DJKeys on 20 Jul 2022, 01:20, edited 1 time in total.

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Re: Lead A1 Pulse Wave Out Of Tune

Postby Mr_-G- » 20 Jul 2022, 13:02

Hi DJKeys, yes, you are right with the LPF.
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Re: Lead A1 Pulse Wave Out Of Tune

Postby Mr_-G- » 20 Jul 2022, 14:21

Actually I checked this in Audacity and Shape=0 generates a square wave (well not exactly, but it is symmetrical, not an extreme pulse as I thought) and increasing the value makes the positive part of the wave wider (so exactly the opposite of what I thought).
Interestingly the fundamental is always there, regardless of the shape setting, but the harmonics are obviously not the same and at low frequency that makes it sound odd. Not broken, not a bug, just a psychoacoustic effect. 8-)

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Re: Lead A1 Pulse Wave Out Of Tune

Postby Kaffimusic » 26 Jul 2022, 15:34

I regret you did not play an octave or 2 simultaneously. This is an effective way to hear detuning between them (beating). Since you think the tuning goes off when going lower. You also did not demo it together with a different waveform to hear detuning beween them.
The wave alone on it´s own is hard to determine, unless you are a person with perfect pitch. I am not, so I can neither confirm nor disagree.
PW tend to sound a bit off when played on low ranges, this does not mean that it is.
I do not own a lead, but I had a Stage 3 which has a scaled down version of the A1 synthengine. In fact I found out the when using "one OSC" as sub there was some slight detuning by software in it, since there was beating, cancelling out high frequencies and so changing the sound in it´s rhythm, although nothing was set. Did not sound nice. But it was just a very small amount and only audible in this configuration.
The thread was here: nord-stage-forum-f3/strange-filter-behavior-t20549.html?hilit=osc%20out%20of%20tune

But, in that case it was just a very small amount, and nothing you would ever notice when played alone - as you did. Only in concert with another one. I guess they did this on purpose, because in most cases it would just trick you to think it sounds fuller. Because - detuning. By force.

Maybe you are right and the Pulse loses tuning when going down (more than just that amount of fake "look, I sound analog!") then indeed it is a technical problem. Until now I guess it is hard to determine if it is or if you are just fooled physics and wrong assumptions.
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Re: Lead A1 Pulse Wave Out Of Tune

Postby Mr_-G- » 27 Jul 2022, 19:54

It does not lose tuning, and the absence of perfect pitch can be conveniently replaced with a spectral analyser. ;-)
The out of tune effect seems to arise when the ear locks into another harmonic instead of the fundamental when playing the lower C.
When playing the higher of the first of the two C notes, the fundamental is around 62 Hz, while when playing the second note one octave down, the fundamental is now 31Hz, which is close to the response of most equipment and also human hearing (about 20Hz). However there is a harmonic which is perceived much louder, at around 93Hz, not what one is expecting when playing down an octave and hence it sounds out of tune. The 31Hz signal is still there, just perceived much less. The waveform does not change shape either, the frequencies should all be there.
Another interesting test is to try the sine wave in the FM mode and play down at 60Hz and 30Hz. The low note becomes difficult to perceive but the peak in the spectrum is still detectable.
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