[BUG] FM + Delay + Reverb = pitch chaos

    Try the following:
    - Use a new Init patch
    - OSC 1 Sine: Transpose + 36
    - OSC 2 Square: Transpose 0, Detune 0
    - Phase Init: 38
    - FM Amount 43%
    - OSC Balance 100% (only OSC 2)
    - Transpose + 12
    - Analog Boost 0


    Play notes in the C3/C4 octave:
    --> everything sounds fine, pitch is correct



    Now add
    - Activate Delay: Simple Delay, Clock 1/8, Feedback 32%
    - Activate Reverb: Large Room, Decay 68, Damping 15.6%


    Play notes in the C3/C4 octave:
    --> for some notes the pitch is totally off, and if those are held then there's playing some sort of pitched sequence which eventually resolves to the correct pitch and stays there.



    Patches to test attached.

    Dateien

    FM+Delay+Reverb Bug.mid.zip 434 Byte – 3 Downloads

    Bass Player and Synthesist.
    Virus TI2 Darkstar | Virus TI2 Desktop | Sub 37 | Voyager RME | Machinedrum | Analog Four | Digitone | MPC Live | NI Maschine+
    Mac OS 13.5.1 (Ventura) | Cubase Pro 11.0 | Ableton Live 9.6 | Logic 10.4 | MainStage 3.4 | NI Komplete Ultimate 13 | RME Fireface UFX+

    Einmal editiert, zuletzt von ozon ()

    Zitat von psylence

    Can you post an audio clip? I think it sounds fine here...


    Edit 1: there's chaos here at D5+...it sounds like a really fast telephone


    That's exactly what I mean! I had that happen mostly on F4, F#4 and G4 (I think, not 100% sure about the correct octave description, but on the Darkstar in the middle octave without transposition)


    PS: For me it happens mostly when playing those notes in a line with other notes.

    Bass Player and Synthesist.
    Virus TI2 Darkstar | Virus TI2 Desktop | Sub 37 | Voyager RME | Machinedrum | Analog Four | Digitone | MPC Live | NI Maschine+
    Mac OS 13.5.1 (Ventura) | Cubase Pro 11.0 | Ableton Live 9.6 | Logic 10.4 | MainStage 3.4 | NI Komplete Ultimate 13 | RME Fireface UFX+

    This "telephone" thing though is not happening when FM is not enabled. I dont think its the combination of FM/delay/reverb; the same telephonish sound is still there beyond D5 even with delay and reverb disabled.


    I'm not an expert in FM (I'm still trying to really understand the difference between FM and pitch modulation:p) but it sounds like D5, i.e. the note where chaos is initiating, is sort of a cutoff point for FM to act much more fast...i'm not even sure if this this audio result is "correct" or if this is a software bug.


    You can reduce the rate of FM though (OSC 1 semitone) to +24 and its fine for all notes!

    Zitat von psylence


    I'm not an expert in FM (I'm still trying to really understand the difference between FM and pitch modulation:p) but it sounds like D5, i.e. the note where chaos is initiating, is sort of a cutoff point for FM to act much more fast...i'm not even sure if this this audio result is "correct" or if this is a software bug.


    Thanks for checking. It just happened again yesterday while experimenting with a very simple FM sound. No Reverb involved. Naturally, FM will have undesirable results if too close at the sample rate. But there's clearly notes which are fine under some condition, and start to "telephone" under others. And yes, it's clearly connected to FM, that's the precondition.


    IMO, since it happens at random, depending on circumstances, depending on settings of other (unrelated) sections of the synth it must be bug.

    Bass Player and Synthesist.
    Virus TI2 Darkstar | Virus TI2 Desktop | Sub 37 | Voyager RME | Machinedrum | Analog Four | Digitone | MPC Live | NI Maschine+
    Mac OS 13.5.1 (Ventura) | Cubase Pro 11.0 | Ableton Live 9.6 | Logic 10.4 | MainStage 3.4 | NI Komplete Ultimate 13 | RME Fireface UFX+

    Could it be just DSP overload?


    And good question about the difference between FM and pitch modulation! The only difference on my Blofeld (easier to check!) is the same LFO modulation amount is much more affective to Osc FM than to Osc Pitch Mod destinations. (Update!: This is because the Blofeld LFO amount applied to Osc FM is exponential but applied to the global Osc Pitch param it is linear. The actual difference is that FM is usually understood to be in the audio range (which Blofeld LFOs are capable of) while just simply "modulation" is not, as stated below.)
    Cheers!

    Zitat von GESchwalm

    Could it be just DSP overload?


    I don't think so! The complexitiy of the patch is indicate with one bar (lowest load) and wha would the CPU be overloaded playing some notes but not others.


    Also there's no voice stealing going on when other sounds are played as well.


    Definitely something wierd with FM (and I had it yet agin on another patch)

    Bass Player and Synthesist.
    Virus TI2 Darkstar | Virus TI2 Desktop | Sub 37 | Voyager RME | Machinedrum | Analog Four | Digitone | MPC Live | NI Maschine+
    Mac OS 13.5.1 (Ventura) | Cubase Pro 11.0 | Ableton Live 9.6 | Logic 10.4 | MainStage 3.4 | NI Komplete Ultimate 13 | RME Fireface UFX+

    BTW, talking of FM:


    FM = Frequency Modulation
    Pitch = Frequency
    Frequency Modulation = Pitch Modulation



    Funny to explore with synths that allow LFOs to go into audio range (e.g. the Sub37) :)

    Bass Player and Synthesist.
    Virus TI2 Darkstar | Virus TI2 Desktop | Sub 37 | Voyager RME | Machinedrum | Analog Four | Digitone | MPC Live | NI Maschine+
    Mac OS 13.5.1 (Ventura) | Cubase Pro 11.0 | Ableton Live 9.6 | Logic 10.4 | MainStage 3.4 | NI Komplete Ultimate 13 | RME Fireface UFX+

    So basically you could say that frequency modulation is modulation with a source that operates in the audio range, as opposed to just modulating something (such as pitch that we mentioned) with a non-audio range source.
    Since FM affects pitch much more drastically than non FM modulation, then I guess it would indeed be appropriate to say FM is pitch modulation on steroids! :>)

    I could be wrong, But is the issue your facing just distortion? FM means that youre essentially adding an audible oscillator with the intention of having said oscillator modulate the pitch of your preexisting oscillator(s). Just using one wave to move another wave. When this happens its easy to interfere with things like reverbs and delays, as those often carry frequency dependent information, and thus disrupting (modulating) the frequencies those are receiving info from will often create distortion of sorts. particularly when the modulation adds amplitude, as is often the case with FM.


    With that line of thinking I think it would make sense that FM would mess with different notes in different ways, depending on the way the frequency of the modulated is affected by the frequency of the modulator, and how the FX that source their frequency dependent information from the modulated, are affected by the modulator. I dont have a whole lot of FM experience, but for me its always been a powerful beast that requires a very intentional placement to be properly tamed.

    Thank you for giving this issue some thoughts!


    Zitat von Coollin

    I could be wrong, But is the issue your facing just distortion?


    I don't think so, at least not in a typical "audio distortion" way. If it happens, certain notes will sound like whole chip tune melodies before settling on the final (correct) note. And it also happened on very simple patches while I was exploring FM without any effects on. But you could be right with your assumption that the added amplitudes produce some sort of overflow which lead to completely wrong results for the calculated waveform.

    Bass Player and Synthesist.
    Virus TI2 Darkstar | Virus TI2 Desktop | Sub 37 | Voyager RME | Machinedrum | Analog Four | Digitone | MPC Live | NI Maschine+
    Mac OS 13.5.1 (Ventura) | Cubase Pro 11.0 | Ableton Live 9.6 | Logic 10.4 | MainStage 3.4 | NI Komplete Ultimate 13 | RME Fireface UFX+

    My next guess would be either an LFO or Filter envelope, but it seems that wouldnt be the case if youve experienced it in bare bones patches. Are you always using square waves when it happens? How about some other form of pitch modulation such as transposition? It could very well be a bug, the virus has a handful, and Iv encountered a few instances of strange and seemingly random things happening to my sounds. But I always wanna give the virus the benefit of the doubt and hope I can learn something about synthesis while investigating.