Can We Get a Frequency Shifter?

[drbob1]

Frequency shifting is using basically the same technology as a ring modulator, except not using the lower sideband and with 100% wet mix: you add the chosen frequency interval to the input note, shifting it up or down by a fixed, not harmonic, frequency. 

One could use the ring modulator except for two problems:

1. You can't get 100% synthesized signal (the sum)

2. You can't enter negative values for the frequency shift

In fact, in a fully featured frequency shifter, you'd be able to add both positive and negative values of the chosen shift, as well as controlling the shift with envelopes, LFOs etc. In case anyone is confused, pitch shifting is moving notes up and down by a proportional interval so they remain musical notes, this is shifting by a fixed interval so there's no harmonic relationship between the input note and the result.

[brock]

I had/have an original run EHX Frequency Analyzer, and updated it with a Ring Thing.  Not enough in the bank for a Bode or modular synth module.  The F/A was an interesting effect, if limited in mainstream applications.  Noisy with age & tone suck, though.

I know where you're coming from with the SSB shifting and modulation.  The Tune function alone (found in the newer EHX) would be a great addition to any Eventide design.  Doesn't the Ring Mod algo have some type of Sync to Pitch?

In the PitchFactor / H9, I get pseudo-frequency shifting effects with the H910/H949 algo (MODERN Depth; NORMAL Scale), or the PitchFlex algo.  It doesn't produce quite the same effect on the harmonic relationships, but it's interesting (and clangorous) nonetheless.  Especially with two pitch shifters sweeping in opposite directions, experimentation on the rates of change & ratio between them, or the Hxxx 'vintage model' selected.

[Bodde]

brock:

 The Tune function alone (found in the newer EHX) would be a great addition to any Eventide design.  Doesn't the Ring Mod algo have some type of Sync to Pitch?

Yes I love ring modulators! A tune option would be a great addition. Manual says that the Ring Mod has sync to pitch. But I can't find it! Where is it in the Ring Mod?

[brock]

bodde:

Manual says that the Ring Mod has sync to pitch. But I can't find it! Where is it in the Ring Mod?

You got me.  The manual seems to imply that switching to Tempo On changes the "LFO rate" (SPEED in H9 Control) from frequency in Hetz to note values  I tried a lot of combinations during the 5-minute trials, and couldn't get that feature to come up.  And it seems like the Modulation Depth is "un-used" in any situation.  Could be user error on my part, an H9 Control quirk, or maybe it goes back to the ModFactor original.

That's not to say that I couldn't tune roughly to a base note frequency with the Speed control.  But that's not the same as a Tune control that could be triggered from a switch or pedal, and "played".  Hmm.  All this talk of frequency shifters and ring modulation will have me dusting off the old Frequency Analyzer for comparisons.

I'll hand it to Eventide's Ring Mod demo presets: They have that barely-on, tremolo and phasing FX from ring modulation well covered.  At least as good – and possibly much better –  than the Ring Thing equivalents.  I know for sure when I finally Max Out on the algorithms.

[drbob1]

Dooo Eeet, and get back to us!

[brock]

I’m exhuming this thread after almost a year, but it seems like the best place to drop this ‘happy accident’ preset.  I stumbled upon some unusual frequency shifting with the Reverse algorithm.  Yes, the one from the TimeFactor.  Yes.  It’s a delay algo.

Mostly WET MIX here (with just enough dry signal to audibly detect the source).  No DELAY time, no FEEDBACK, no FILTER, … simply working the XFADE to tune the approximate ‘tonal center’ for the frequency shift.  [Note: XFADE can get awfully glitchy when mapped to an expression pedal.  Which makes perfect sense, considering what it controls.]

Dialing in 3 mS to about 14 mS in XFADE will change which input notes are relatively consonant.  Fine-tune the XFADE range with mouse movement + CTRL / Cmd key [in H9 Control].  Glide along the fretboard / keyboard to locate the ‘root’ for any millisecond value.  The shifted sideband will move in the opposite direction of your input notes.  String bends and vibrato do the same (bend up = sideband bend down).  There’s an element of chaos in these adjustments that’s part of the charm.

From 15 mS on up, XFADE injects more tremolo effects at slowing rates, but with enveloping and vibrato / pitch shift.  From 100 mS to 200 mS … Electric Ladyland.  DEPTH MOD and SPEED work in unpredictable ways; depending on the current XFADE value.  Turning DELAY B up to several dozen milliseconds adds more modulation possibilities.

[DGillespie]

Hi Brock,

 

If you're interested in reading a bit more about the effect you've stumbled upon, there's information here.  https://www.ntnu.edu/documents/1001201110/1266017954/DAFx-15_submission_5.pdf/09f59775-5d01-4699-99ee-995b23dedea4

Sorry I didn't notice this thread the first time it popped up.  The Ring Modulator does indeed quantize to half steps when you turn tempo mode on.  The display still shows the value in Hz, but you'll notice that the step size changes, and as you sweep it you should hear that it's jumping by half steps.  For instance you can pull it directly to 440, and that will be an A.

Dan

 

[brock]

I appreciate the expanded information, Dan.  I would’ve never thought ‘spectral aliasing’.  The sidebands come across so clear & ‘pure’ (clangorous).  If you don’t mind, can you expand on some specifics, as implemented in the Reverse algorithm?

• The STTR window would be the XFADE value in milliseconds?  It seems to me that the signal will be reversed no matter what, but over an adjustable duration.  That is, it’s not directly related to the current DELAY time parameter values [0 mS here, but no doubt some fixed processing time].
•  
• Modulation appears to be hit-or-miss in this config.  Certain XFADE values can produce an irregular ‘whammy bar bump’, but only at specific SPEEDs (DEPTH MOD up, of course).  Fractional Hz. can reveal 3-4 discrete ‘pitches’.  I’d have guessed modulation injecting a predictable effect at these settings, so perhaps there are other contributing factors here?
•  
• Is it coincidental that the sidebands are produced in windows less than 30 mS (also commonly cited as near the threshold where human hearing perceives sounds as distinct events)?

I’m going to refrain from a discussion on XFADE values to 3 decimal places.    Thank you for ‘chiming’ in here.

[DGillespie]

The STTR window length would be the DELAY time plus the xfade length.  The window Overlap would be the xfade length.  That said, this will result in odd shaped windows.  If you set delay to 0mS and then the total window length will be 2*xfade (this is because 2*xfade is actually the shortest delay possible) and will actually form a Bartlett window.

 

Modulation will effect the delay time which will, in effect, modulate the window length (when delay > xfade) and shape.  I'm not entirely sure what this will do to the percieved effect.

 

Sidebands are always created when you amplitude modulate a signal (which you are doing here by the window function), but it's not coincidental that you start hearing the sidebands around an xfade length of 30 mS (which corresponds to a window length of 60 mS).  This is because 1/60mS is 16.6 Hz, which is close to the lower limit of human hearing.  As you shorten the window length you essentially raise the frequency of this triangle wave, moving the sidebands further apart and they sound more distinct.

 

This STTR effect is obviously not the intent of the reverse delay algorithm, but it's an interesting curiousity and it's fun to think through the ramifications of the effect.  My gut says that most of the effect is simply from the multiplication of the fast triangle wave with the input signal, which is essentially a ring modulator, but as the paper shows, reversing the audio inside each window does create it's own effect.

Dan

 

[brock]

Thank you for that answer.  It was very generous on details.  I know this was never the focus with the Reverse algorithm, but discovering some untapped potential inside these algorithms always puts a smile on my face.

And then I want to know more about how and why it works that way (which leads to another discovery …)

[Author]

Posts