AKWF single cycle waveforms question

I think your right about it being a problem with the tuner, that its possible aliasing throws the tuner off and that the tuner may be optimized for guitar frequencies. I used it to try and check the pitch of some of the AKWF fm waveforms and it could not even register that a note was playing.
If I use the perfect waveforms the note always shows.

thanks, your right...in theory the pitch should stay accurate as Im using SCWFs and not other types of short loops or one shot samples spread across the keys..."difference in pitch in terms of cents stays about the same, but as you go up the scale the difference in terms of Hz grows"

Although the guitar tuner was registering flattened notes I couldnt make out whether the notes I was hearing were flat or not by ear.
Thanks for the tips about sample frequency and phase increment.

I sent adventure kid an email asking about whether the D2 is raised by 2 cents or what he meant by "+2". If I get a reply I'll post the answer here. I should buy a more accurate tuner for future use. Thanks for all your help. Much appreciated

Last edited by Mister Sombrero (Jul 3, 2013 3:50 pm)

Thanks for the link. That will be very useful

being a scientist, i can't resist to bore all of you with some theoretical details regarding this
especially for fm sounds is makes perfect sense for the tuner not to register the basis frequency at all, if you consider how fm spectra differ from those created by a plucked string instrument. for plucked strings, you always get the strong "base frequency" (first mode of oscillation) and only the overtones above that (being integer multiples of the base freq). an example can be seen at the bottom of this page: fixed string vibration
fm spectra look kinda different, as can e.g. be seen here: fm spectra in the second picture. first, the spectrum is always symmetrical to the base frequency, and second, depending on the modulation index, the amplitude of the base frequency might be smaller than that of the sidebands (look at modulation index 2 in that picture, for example). in addition, you might get aliasing effects if the sidebands go above/below the possible range of sampled frequencies.
hence it's not surprising that the tuner which probably just looks for the lowest/maybe strongest frequency component has a hard time recognizing the base note.

Sorry for the double post here.

I tried my guitar tuner with renoise and every note using renoise's included chip instruments registerd as being perfectly in tune (including FM sine).

LGPT oscillator tuning test 1

I took the A440 test tone sample from http://onlinetonegenerator.com/...
I reduced it to a mono single cycle waveform.
I loaded it into LGPT.
Switched to oscillator mode (loop end was 64 / 100decimal).
Notes played in tune if root note was set at C2.

LGPT oscillator tuning test 2

basic waveform samples taken at A440 from audiocheck.net (440Hz, 1 sec, -3db, 8Khz).
Cut them down to single cycle waveforms using renoise, chopping at zero crossing to get exactly 1 cycle.
Loaded them into LGPT.
Changed to oscillator mode...(loop end was 12 / 18decimal), Root note was A...
every note played out of tune...
Changed to root note C...still out of tune (consistently by one semitone)..
After I changed the root note to Csharp every note played perfectly in tune.

LGPT normal loop mode + oscillator mode tuning test

Extracted the single cycle waveforms from renoises included chip instruments (triangle smooth, triangle complex, chip triangle, chip square, chip sine FM, chip sine, chip sawtooth, chip saw smooth)

They will be in tune in normal loop mode if root note is C3.
They will be in tune in oscillator mode if root note is C6.

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if LGPT expects A440, root note C in oscillator mode...the renoise single cycle chip samples should be more out of tune in normal loop mode as the root note was C and not A.

Also these waveforms were behaving really strange in terms of tuning:

basic waveforms at A440 from audiocheck.net (440Hz, 1 sec, -3db, 8Khz) loop end 12

(because they played absolutely perfectly in tune across all octaves and notes, but only if root note was Csharp)...WTF?

Last edited by Mister Sombrero (Jul 5, 2013 4:25 pm)

The C# thing looks fishy indeed.

One thing that is important to understand is that the very goal of the oscillator mode (in theory) is not to have to care about the note that was originally played when sampling the cycle. So if you have a single cycle sampled from an A4 note, to get correct pitches you need:

+ In regular loop mode, you should set the root key to A4 to get correct pitches (like in regular samplers)
+ In oscillator mode, you should *leave* root key to C. The oscillator mode re pitches the sample data automatically so it's tuned.

This doesn't explain the case you have where you need to put root key to c#. If you want to send me the project you are using, I could look at it.

Note also that the oscillator mode has been know for heaving tuning quirks since the beginning. It's not enormous but it's there. If I remember well, I had found a way to fix it but most of my song turned into uninteresting mud so I decided to keep it that way.

Hope this clarifies the situation a bit

I think you called it PFIN.