I'm using this module to create percussive patterns with the LFO:

Noise module front panel

As you can see the frequency can be synced with the clock of the host DAW:

Reactor modules of the LFO section

What I'd like to be able to do is to shift the phase of the LFO so that the user could, for example, shift between this:

LFO phase in sync

and this:

LFO phase shifted

Horizontal bars represent steps in the host sequencer.

I believe that "sync" might come into play here, and my understanding of sync would be that when implemented, the start of the LFO wave begins again with every new pressing of the key.


There is a sync input, which, when creates a button control you can set to "toggle".

And a SyncPhase, which I would expect does what I want. It says that with values between -1 and 1, the phase can be shifted between -180 and +180 degrees.

The Sync Phase controls in the module

LFO Panel with sync controls

However I am still unable to shift the phasing of the amplitude around the sequencer steps as I want to.

Even stepping away from the DAW clock. I would expect that, with

  • sync toggled to "on" (min:1, max:1)
  • LFO amplitude at max (1)
  • Pulse wave operating on amplitude

That with SyncPhase at either -1, 0, or 1, the "on" phase of the amplitude LFO would occur when the gate opens (pressing the keyboard).

It's seems as if sync isn't engaging at all.


As per the (soon to be) accepted answer below, I have updated the way the LFO module is configured so that it's output is multiplied with the oscillator output (as opposed to receiving it at the A input).

New configuration of LFO module

And implemented the recommended module, with the LFO amp knob going from 0 to 1.

Implementation of solution

However I'm still not getting what I want, where I can shift so that the "on", or 1 phase of the LFO is concurrent with gate opening. Like I would think that

  • with sync toggled on,
  • frequency setting very slow
  • Amplitude at 1 (all the way on)
  • if I press a key repeatedly without sustain
  • while turning the syncPhase knob
  • it will shift between always and never making a sound
  • in other words between [silent-sound-silent-sound] and [sound-silent-sound-silent]

But it still isn't doing that.

  • Is the SyncPhase setting also available when the Source is set to Clock? – Tom Jun 26 '20 at 13:18
  • Yes, @Tom_C. It is. And that makes me realize that the feed for the knob input on the switch should not be multiplied by the clock. However the problem is still there. I cannot seem to SyncPhase shift so that the #on# phase occurs upon gate open. – MikeiLL Jun 26 '20 at 13:57
  • (Wild guess, I am not using Reaktor): are you sure Reaktor is able to dephase a square wave? If this phase is implemented as a biais value, you have effectively a phase change for a Sin, but not for a square… – Tom Jun 27 '20 at 20:13

The sync inputs of the various oscillator and LFO modules expect an audio signal or another signal that alternates between negative or zero and positive; when the signal changes to positive, the oscillator is retriggered.

The easiest way to sync an oscillator to the MIDI clock is to use the Sync Clock module. Its output alternates between a value that you can set in the properties (e.g. 1) and zero, and you can select whether it follows the clock in 1/4 notes (beats) or 1/8, or 1/16 ...

Reaktor structure

In this example the Sync Clock signal is multiplied with the value of the Sync button which toggles between 1 and 0, to switch the synchronization on or off.

Reaktor panel

You also have to take into account that the output of oscillator and LFO modules varies between +A and -A. If you want to use the output to modulate the amplitude of an audio signal (i.e. multiply it with the audio signal), set A somewhere in the range 0 ~ 0.5, and add 1 - A to the output. This will result in the output varying between 0 and 1 if A is set to 0.5, and a fixed output of 1 if A is set to 0. (Output marked with x)

If you want to use the output to modulate the pitch of an oscillator or filter (where a value is alternately added and subtracted from a center value) don't add anything to the output of the LFO (output marked with +). You can multiply this output further down the line, before adding it to a pitch signal, to set the depth of the modulation effect.

If you want the LFO to run at the same frequency as the clock, but sync it to the key presses, you could add another switch module to select between the Sync Clock and the Single Trigger Gate as the source of the sync signal.

Reaktor structure

Then you can set the tempo of the LFO to either the MIDI clock or manually with the panel knob, select the sync source independently, and use the Sync Phase knob to select which part of the LFO waveform you want to start with when a key is pressed or the MIDI clock changes to positive.

Reaktor panel

If this is used in a polyphonic instrument, the Single Trigger Gate may not behave as you want it to, in which case you could replace it by either the regular polyphonic Gate module (and make the whole LFO macro polyphonic) or the All Key Gate macro from my answer about portamento.

  • I believe I have recreated your example. 1 Source is between Tempo Info and Freq. 2. Amp knob from 0 to 0.5, divided by 2 and split to A input of LFO, then subtracted from 1 and re-added to LFO output. 3. This (x) output is multiplied with output from a noise osc. RESULT Following the 1-A the connection reads as inactive. – MikeiLL Jun 28 '20 at 14:52
  • @MikeiLL I'm only dividing by 2 because the knob goes from 0 to 1 (that seemed more logical as a user interface). If the knob goes from 0 to 0.5, you don't need to divide it. The inactive problem sounds like a mixed mono/poly problem; make sure you don't have poly signals feeding into mono modules. – Your Uncle Bob Jun 28 '20 at 15:47
  • Updated the question with my implementation. The cause of inactive was having assumed that the output that was higher up inside the module corresponded to the higher one outside. I had named them with the same first few letters. However, out outlined above, it still doesn't seem to work as desired. – MikeiLL Jun 28 '20 at 18:23
  • @MikeiLL When you talked about syncing and the MIDI clock, I assumed you wanted the LFO synced to the clock. As I understand it now, you want it to have the same frequency as the MIDI clock, but sync it to the key presses? – Your Uncle Bob Jun 28 '20 at 20:51

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