[sdiy] Simple (?) sequencer mod for syncopation

[David G. Dixon]

I thought it might be nice to have a little break from the physics of
sigmoid waves, so here's something musical and synthy to consider.

I'm in the process of beginning to organize a 16-step sequencer for my
ever-growing modular, based on Ray Wilson's famous circuit with Thomas
White's brilliant circular front panel layout (only mine will have a panel
board to eliminate a whole bunch of wiring).

Coupled with this activity, I've been listening to various synth-based music
in my car, including Herbie Hancock's classic "Headhunters" album.  The
opening of the famous first track "Chameleon" (many of you probably know it)
involves a sequence of 12 notes.  However, the sequence would require a
32-step sequencer clocked in the normal way, because the sequence is over
two bars, and those bars each must be subdivided into 16th-notes to capture
the funky rhythm of the sequence.

Now, coupled with these thoughts, I have just been reading Allen Strange's
book, "Electronic Music: Systems, Techniques, and Controls (1972 ed.)."  In
the excellent Chapter 6 on "Gating" (page 44) he talks about something
called "pulsed mixing."  In this technique, one takes a pulse wave, isolates
the positive and negative parts, and uses them separately to gate two VCAs
processing different signals, causing anything from a jarring "ping pong"
effect to a seamless blending of the two.  I find this very intriguing.

This got me to thinking: Why not "pulsed triggering?"  One could take a
standard 16-step sequencer and feed it with two clock signals, both derived
from the same pulse wave.  One signal would consist of rectified pulses from
the clock wave, and the other signal would consist of rectified pulses from
the inverted clock wave.  Hence, one would have 32 triggering pulses at ones
disposal.  Each step of the sequencer would be provided with an extra switch
for selecting whether that step is triggered by the (first) "rectus" pulse
or the (second) "inversus" pulse.

Now, going back to Herbie Hancock's "Chameleon" sequence, starting at the
downbeat (i.e., the fourth note of the opening), here is the succession of
notes (/) and rests (-) over the two bars:

/--/--/---/-/-/-/--/--/---/-/-/-

As you can see, there are 32 events here, but only 12 notes.  If each pair
of events corresponds to a single step of a 16-step sequencer, then here is
the sequence of pulse selections for all 16 steps (R = rectus, I = inversus,
X = don't care (no note on that step):

R I X R X R R R R I X R X R R R

So the 16-step sequencer has been tricked into becoming a virtual 32-step
sequencer (albeit with only 16 notes).  The only caveat is that one could
not have three notes in a row without at least a 16th beat rest between two
of them.  However, within this limitation, the funky possibilities are
nearly endless.

Finally, pulse width modulation of the clock wave gives "swing" as well as
syncopation (Thomas White has already done something like this, bless him!)

Discuss!