Kurzweil KDFX, Manual

Page: 73 / 164

Real-time Control of KDFX
Tempo-based control of KDFX
4-17
Tempo within an FX Preset
Some Algorithms have a ÒTempoÓ parameter, which allows certain time-based functions, such
as LFOs, envelopes, or delay lengths, to be expressed in beats per minute (BPM). A second
parameter immediately below Tempo, ÒPeriodÓ, multiplies or divides the tempo. The Period is
expressed in beats (ÒbtsÓ) and ranges from 1/24 (the actual time is 24 times faster than the
Tempo) to 32 (the time is 32 times slower than the Tempo) in a sliding scale based on 24ths of a
beat. So for example, if an LFO has a Tempo setting of 120 BPM and a Period of 12/24 bts, the
LFO will oscillate 240 times per minute, or 4 Hz.
The formula for converting tempos and beats to frequency values is:
Ä in Hz = (Tempo in BPM/60) x (number of beats per period), or
Ä in Hz = (Tempo in BPM/60) x (1/bts).
The formula for converting tempos and beats to time values (e.g., delay lengths) is:
T in seconds = (bts/tempo) * 60
Variable tempos using ÒSystemÓ
You can also have these parameters respond to tempo in real time, by setting the Tempo
parameter to ÒSystemÓ, which is set by scrolling below 1 BPM (or pressing Ò
0 Ó and Ò Enter Ó on
the numeric keypad). Now instead of Tempo being a Þxed value, it will vary according to the
system clockÑwhich, depending on the setting of the Clock parameter on the
Song modeÕs
MISC page as described above, will either be the internal sequencerÕs clock, or tempo coming
from an external source of MIDI Sync. The System Tempo will be multiplied or divided by the
Rate or Beats setting, to determine the parameterÕs actual speed, just as if it were a Þxed value.
If the Clock setting is ÒIntÓ, then the current tempo of the internal sequencer (as shown on the
Song ModeÕs
MAIN page) will be in effect whether or not the sequencer is running .
If the Clock setting is ÒExtÓ, the external sequencer (assuming it is sending MIDI Timing
Clocks) controls the Tempo parameter. If
no MIDI sync is being received by the K2500, the
tempo will not go to Ò0Ó; instead, it will retain the last valid value it sawÑeither the tempo of
the internal sequencer at the time when you switched the Clock to ÒExtÓ, or the last tempo sent
by an external sequencer before it stopped.
Tempo as an FXMod Source
KDFX Algorithms that donÕt have a ÒTempoÓ parameter can also respond to tempo
information, using FXMods.
In the Control Source list, there is now a parameter called ÒTempo,Ó located at number 55. You
can call it up quickly by pressing
5 - 5 - Enter on the keypad, or holding down the Enter key and
playing A b below middle C on the keyboard.
This source reads the current tempo (Þxed or variable, internal or external) and turns it into a
numerical value between 0 and 1, which is then used to scale the Depth value of the parameter
under the control of the FXMod. The ÒvirtualÓ range of this parameter is 3.75 to 240 BPMÑthat
is, a tempo of 3.75 BPM (or less) will scale the Depth parameter value to 0, while a tempo of 240
BPM (or greater) will scale it to 1, or its highest value.
This may sound confusing, but there is a relatively simple method to follow when using this
feature: set the ÒAdjustÓ value of an FXMod to the value of the parameter that you want when
the tempo is 3.75 BPM, and set the ÒDepthÓ value so that the sum Depth equals the
value that you want when the tempo is 240 BPM.