MOTM

While awaiting arrival of my MOTM modules, I've been meditating on 
functional density in modular synthesizers.  I've always operated on 
a feeling about how much tonal richness I could get from a set of 
modules, which had to do roughly with the quantity of activity going 
on all at once.  This is directly related to the number of distinct 
signals available.  The richness also has to do with the number of 
voltage-controlled parameters that are being modulated 
simultaneously.  

I came up with a simple way to quantify the functional density of a 
module as follows.  It is the number of distinct signal sources 
produced by a module plus the number of independently variable 
voltage-controlled parameters afforded by the module, divided by the 
panel width.  Here's the breakdown for MOTM.  

MOTM    MODULE  SOURCES PARAMS  WIDTH   DENSITY
-----------------------------------------------
101     S&H     2       0       2       1
120     SUB     0       0       2       0
190     VCA     0       2       1       2
300     VCO     1       2       2       1.5
310     VCO     1       2       1       3
320     LFO     1       2       2       1.5
380     LFO     4       0       1       4
390     LFO     2       1       1       3
410     VCF     2       3       2       2.5
410     VCF+OMS 2       6       3       2.66
420     VCF     0       1       2       0.5
440     VCF     0       2       2       1
480     VCF     0       2       2       1
490     VCF     0       1       1       1
700     ROUTER  0       2       2       1
800     EG      0       0       1       0
820     LAG     0       2       2       1
830     MIX     0       0       2       0
850     PEDAL   0       0       1       0
890     MIX     0       0       1       0

My rational for counting sources: The 101 S&H has one noise source, 
plus one clock.  Even though filters can oscillate, I'm not counting 
that as a source.  I don't count multiple waveforms coming from the 
same oscillator.  

Most of this is not too surprising.  The quad LFO in a 1U panel has a 
high functional density.  Modules that do static processing, such as 
envelope generators and mixers have zero density, which means that 
when added to a system simply lower the overall density.  To me that 
gives them a lower value.  But then I seem to be obsessed with 
functional density!  

This analysis did produce a few interesting results.  The 310 micro 
VCO has twice the functional density as its big brother, the 300, 
because it has the same number of sources (1) and parameters (FM and 
PWM), but in half the space.  That's the idea, I suppose.  

The 410 Triple Resonant Filter has a high functional density due to 
the internal dual LFO, which adds two sources.  The 410 also has 
three independent parameters: combined filter frequency (sweep), LFO 
rate, LFO internal modulation depth.  Let's add the OMS-410.  Now 
there are six parameters: 3 independent filter frequency controls, 
LFO rate, internal LFO depth, external LFO depth.  This is based on 
the MOTM-standard option panel for the OMS-410.  But wait.  Now it's 
3U wide.  Doing the math shows that adding the OMS-410 increased the 
functional density only a tad from 2.5 to 2.66.  But I like getting 
those extra three parameters to control.  Notice that this analysis 
does not quantify the aspect of having the LFO outputs available 
externally.  Making the LFOs available for input to other processing 
does not add any new sources to the system.  

MY WISH LIST (Hey Paul!)

Being an old Serge guy, I long for the Serge dual slewing module.  
Now, if Paul would make a very minor modification to the 820 Lag 
Processor we would have this.  Put a comparator with big hysteresis 
on the output, so that when the output level reaches maximum (+5v) 
the comparator puts out a -6v.  Now the comparator will stay at -6v 
until the output goes all the way down to -5v, at which point it 
snaps back to +6v again.  So what, you say?  Well, now you now have a 
pulse output.  Patch that output into the lag input and now you have 
an LFO with a voltage-controllable waveshape.  Functional density 
goes up to 1.5.  But even better, I would like to see a micro Lag 
Processor/LFO, fitting into a 1U panel with six jacks and three 
pots.  

Jacks:  Input, Pulse Out, Lag Out, VC Up, VC Down, VC Up-Down
Pots:   Initial Up, Initial Down, +/- Inverting attenuator VC Up-Down 
input

Sources 1, Parameters 2, Width 1, Functional density 3.

I had about eight or so modules of different variants on this theme 
in my original synthesizer (which is now probably gathering dust in 
somebody's attic).  

-Richard Brewster