| Bad_Mister
Total Posts: 36620
Joined 07-30-2002
status: Legend
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Re: LFO questions
This is from a previous post - answering a question on the COMMON LFO and ELEMENT LFO......... The original question was for the Motif ES keyboard - so I made some adjustments for the Rack ES......... hope it is helpful.
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The best way is to dig in and experiment. Let’s get you clear on VOICE mode editing (and all editing in general on the Motif-series).
First thing to know is there are two levels of editing a VOICE: COMMON and ELEMENT. The top line of the screen will always indicate which you are on.
COMMON - you are in Common edit
ELEMENT - you are in Element edit
You use the [MUTE/SEL] button to naviage the operating system. When the LED is ON you can MUTE ELEMENTS. WHen the LED is OFF, you have selected the SELECT function and can switch between COMMON Edit parameters and PART Edit parameters.
_ Use [SHIFT] + COMMON to get to COMMON
_ Use the Number buttons [1/5/9/13], etc to select Elements.
Common edits as the name implies are things that are common to all aspects of the Voice, while Element edits are those that are applied specifically to one of the four basic building blocks of the Voice.
That said, if you explore you will see that there is an LFO in both COMMON and ELEMENT levels. One is the Common LFO (C-LFO) the other is the Element LFO (E-LFO). Yes each Element has its own Low Frequency Oscillator.
A Low Frequency Oscillator is a vibration generator that specializes in creating vibrations at frequencies below the range of hearing. You may know this but I’ll state it anyway… the human ear can hear vibrations between 20 cycles per second and 20,000 cycles per second. We recognize these frequencies as sound. Once the vibrations go above 20,000 most humans can no longer hear them (dogs can)… and once the vibrations go below 20 times per second we no longer hear them as a consistent tone… they become perceived as a rate (separate events).
Of course, you can hear 1 cycle per second. Think of a metronome doing quarter notes at 60BPM click, click, click, click… you can hear it. Yes, the click is about 2k but the rate is once per second. If you increase that rate to 20 times per second you will no longer be able to distinquish individual clicks - they will become a “blur”, a low pitched tone.
Anyway, that’s what an LFO does, it concentrates on giving us rates… like once every 2 seconds, or once every 5 seconds, whatever. We use these rates and apply them to three major components of synthesis.
Oscillators, Filters, and Amplifiers.
Oscillators are responsible for Pitch
Filters are responsible for Tone (timbre)
Amplifiers are responsible for Loudness
Apply an LFO to an Oscillator (pitch) musically is called vibrato
Apply an LFO to a Filter (tone) musically is called wah-wah
Apply an LFO to an Amplifier (loudness) musically is called tremolo
Now to your question.... sometimes changing a single parameter will seeming have no effect. Why? Because it may be a parameter that is biased (dependent on) the movement of a controller. For example, LFO SPEED. You may increase the Speed parameter - but hear nothing because the LFO may only be applied when the assigned controller is moved.
LFO can be applied either “fulltime” or they can be “biased to” a controller… so that only when that controller is engaged do you hear the affect of the LFO… a typical example is the Mod Wheel being the Pitch Modulation Depth controller for LFO. If this is not biased to the MW, then the vibrato would be fulltime (happening at all times) but by assigning PMD to a physical controller you can bring it in and out when you wish.
The Common LFO is quite flexible and very programmable.
Here, from a previous post, is an experiment you can try that will help you learn about the COMMON LFO and controller assignment versus fulltime control
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Best way to learn about this is to look at a Voice that has the CLFO assigned to TempoSync, and see what kind of control you have in this Voice. Call up the Voice USR1:123 “Se:Racer”
This Voice has a USER LFO (it is 16 steps) It is set to cycle at a rate of 16 steps per measure - at 4/4 time is 1 measure per cycle. What you need to know about this Tempo Sync’d LFO is that it is mapped to 3 destinations:
DEST1 - first assignment PMD (pitch modulation depth)
DEST2 - second assignment FMD (filter modulation depth)
DEST3 - third assignment RESO (filter resonance)
PMD is Pitch Modulation Depth = 114
FMD is Filter Modulation Depth = 34
RESO is, of course, Resonance = 23
When Pitch Modulation Depth is set to a value, like 114, it is full time meaning it is not under control of a knob or controller. To hear its contribution to this Voice set the PMD = 0. This will remove it from the equation. You will still hear the contribution of the Filter Modulation and the Resonance but the sense of pitch movement is now gone.
CURSOR to DEST2
Remove the contribution of the FMD by setting DEST 2 = 0 and set finally
CURSOR to DEST 3
Remove the RESO = 0. Now you will have the VOICE without LFO movement of pitch, filter or resonance.
Let’s assign the depth to a Controller Set:
Go to the CTL SET (Control Set) screen.
“Set1”
Set Control Set 1: MW(01) as the SOURCE, and CLFO-D1 (Destination 1) as the DESTINATION - this will now make the MOD WHEEL control the Pitch Modulation Depth. Set the Depth to +60 and move the mod wheel while holding a note. This will allow the wheel to now be the depth control.
Set Control Set 2: MW, CLFO-D2 (which will control filter modulation depth). Set a Depth of +10
Press [SF2] and set Control Set 3: MW, CLFO-D3 (you’ll find it at the end of the list - this will be resonance) Set a Depth of +7
That should give you an idea about how the assignments work. You of course can assign the control of each of these to independent controllers.
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