KnowledgeBase | K2600R | Song Mode/Sequencing


Syncing an LFO to Sequencer Clock

Question:

How can an LFO be synced to the sequencer or external clock?

Answer:
Using the "Tempo" control source

If you have a K2600/2661 or a K2500 with v4 or later of the operating system, you will have a Control Source called Tempo. This Control Source uses the K2's own internal clock or an external MIDI clock as a modulation source (whether you sync to the internal or external clock depends on the setting of the 'Clock' parameter on the SongMode:MISC page - see the TIP section at the bottom of this page for details).

One possible application for the Tempo control source would be syncing an LFO to the sequencer's clock. Here is the basic procedure:

Start by setting the LFO's rate control to "Tempo" and "Shape" to Sine.

EditProg:LFO               <>Layer:1/1  

      MnRate:MxRate:RateCt:Shape: Phase:
LFO1:  0.00H  0.00H Tempo  Sine   0deg
LFO2:  0.00H  0.00H OFF    None   0deg


<more  LFO    ASR    FUN    VTRIG  more>

For eighth notes:

Set the LFO Max Rate to 8.00Hz, set the Min Rate to 8.0/64 = .125Hz (the closest value available is .12Hz).

EditProg:LFO               <>Layer:1/1  

      MnRate:MxRate:RateCt:Shape: Phase:
LFO1:  0.12H  8.00H Tempo  Sine   0deg
LFO2:  0.00H  0.00H OFF    None   0deg


<more  LFO    ASR    FUN    VTRIG  more>

For quarter notes:

Set the LFO Max Rate to 4.00Hz, set the Min Rate to 4.0/64 = .0625Hz (the closest value available is .06Hz)

EditProg:LFO               <>Layer:1/1  

      MnRate:MxRate:RateCt:Shape: Phase:
LFO1:  0.06H  4.00H Tempo  Sine   0deg
LFO2:  0.00H  0.00H OFF    None   0deg


<more  LFO    ASR    FUN    VTRIG  more>

For sixteenth notes:

Set the LFO Max Rate to 16.00Hz, set the Min Rate to 16.0/64 = .25Hz

EditProg:LFO               <>Layer:1/1  

      MnRate:MxRate:RateCt:Shape: Phase:
LFO1:  0.25H  16.00 Tempo  Sine   0deg
LFO2:  0.00H  0.00H OFF    None   0deg


<more  LFO    ASR    FUN    VTRIG  more>

As an explanation, you divide the Max rate by 2, six times, because the tempo control source covers 6 doublings of tempo, from 3.75BPM to 240BPM. The Max rate corresponds to the LFO rate when the tempo = 240BPM.


Notes on Controlling the LFO Rate with a FUN

In the description above on syncing an LFO to the clock, you may have noticed that the values you set for eighth and quarter notes are not the exact values you need. This is due to the limits of resolution values in the K2. However, it is possible to use FUNs to get finer resolution.

The simplest FUN would have to be "a-b" , with "a=Tempo", and "b= .16", because what you want to do is subtract 1/6 = .16666... to slow it by a factor of two to get eighth notes.

EditProg:FUN               <>Layer:1/1  

      Input a: Input b: Function:
FUN1: Tempo    =0.16    a-b             
FUN2: OFF      OFF      None
FUN3: OFF      OFF      None
FUN4: OFF      OFF      None
<more  LFO    ASR    FUN    VTRIG  more>

Then patch FUN1 to the LFO rate control in lieu of the Tempo source directly. Better, but you can see that there is error here too.

To further compensate for the error, you could use:

(for an eighth note LFO)

EditProg:FUN               <>Layer:1/1  

      Input a: Input b: Function:
FUN1: -ON      OFF      (a+2b)/3
FUN2: FUN1     Tempo    a/2+b           
FUN3: OFF      OFF      None
FUN4: OFF      OFF      None
<more  LFO    ASR    FUN    VTRIG  more>

FUN1 = (a+2b)/3, a = -ON, b = OFF (computes -1/3)
FUN2 = a/2+b, a = FUN1, b = Tempo (computes Tempo - 1/6)
and then patch FUN2 to the LFO rate control.

(for quarter note LFO) - change FUN2 to "a+b" to halve the rate again.

EditProg:FUN               <>Layer:1/1  

      Input a: Input b: Function:
FUN1: -ON      OFF      (a+2b)/3
FUN2: FUN1     Tempo    a+b             
FUN3: OFF      OFF      None
FUN4: OFF      OFF      None
<more  LFO    ASR    FUN    VTRIG  more>

(for half note LFO) - subtract 3/6, and patch FUN1 back in again as the LFO rate control.

EditProg:FUN               <>Layer:1/1  

      Input a: Input b: Function:
FUN1: -ON      Tempo    a/2+b           
FUN2: OFF      OFF      None
FUN3: OFF      OFF      None
FUN4: OFF      OFF      None
<more  LFO    ASR    FUN    VTRIG  more>

(tempo - 3/6) = (tempo - 1/2) =>>
FUN1 = a/2+b, a = -ON, b = Tempo

(for whole notes) - subtract 4/6 and patch FUN2 in as the LFO rate control.

EditProg:FUN               <>Layer:1/1  

      Input a: Input b: Function:
FUN1: OFF      -ON      (a+2b)/3
FUN2: FUN1     Tempo    a+b             
FUN3: OFF      OFF      None
FUN4: OFF      OFF      None
<more  LFO    ASR    FUN    VTRIG  more>

(tempo - 4/6) = (tempo - 2/3) =>>
FUN1 = (a+2b)/3, a = OFF, b = -ON
FUN2 = a + b, a = FUN1, b = Tempo

(for double whole notes) - subtract 5/6 and patch FUN3 in as the LFO rate control.

EditProg:FUN               <>Layer:1/1  

      Input a: Input b: Function:
FUN1: -ON      OFF      (a+2b)/3
FUN2: -ON      FUN1     a/2+b
FUN3: Tempo    FUN2     a+b             
FUN4: OFF      OFF      None
<more  LFO    ASR    FUN    VTRIG  more>

(tempo - 5/6) = (tempo - (2/6+3/6)) = (tempo - (1/3+1/2)) =>>
FUN1 = (a+2b)/3, a = -ON, b = OFF
FUN2 = a/2+b, a = -ON, b = FUN1
FUN3 = a + b, a = Tempo, b = FUN2

TIP: Internal vs External Clock Sync Options

When syncing to its own internal clock (Clock:Int)...

SongMode:MISC  Events:375k   STOPPED    
RecMode :Linear Quant:OFF   CountOff:1
PlayMode:Loop   Grid :1/16  Click   :Rec
KeyWait :Off    Swing:0%    ClickCh :16
Locate  :  1:1  Sync :Off   ClickPrg:198
AutoIn  :  1:1  Clock:Int   ClickKey:C 4
AutoOut :  1:1  Tempo:Auto  ClickVel:100
Record  Play   Stop   New   In/Out MAIN 

...the master clock tempo (bpm) is set by the 'Tempo' field on the SongMode:MAIN page.

SongMode:MAIN  Events:375k   STOPPED    
CurSong:1 NewSong            Tempo:120  
RecTrk :1    Vol:127 Pan:64  Mode :Merge
Program:1 Concert Piano 1    Locat:  1:1

Track  :R - - - - - - - - - - - - - - -
Channel:1 2 3 4 5 6 7 8 9 10111213141516
Record  Play   Stop  Erase  MISC  MIXER 

When syncing to an external clock (Clock:Ext), the clock source is derived from the MIDI Clock signal being fed into the K2's MIDI IN port.

SongMode:MISC  Events:375k   STOPPED    
RecMode :Linear Quant:OFF   CountOff:1
PlayMode:Loop   Grid :1/16  Click   :Rec
KeyWait :Off    Swing:0%    ClickCh :16
Locate  :  1:1  Sync :Off   ClickPrg:198
AutoIn  :  1:1  Clock:Ext   ClickKey:C 4
AutoOut :  1:1  Tempo:Auto  ClickVel:100
Record  Play   Stop   New   In/Out MAIN 


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