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There's a particularly interesting group of instruments
called Modular Synthesisers that
lies directly within the intersection between electronics,
signal processing, music and
crazy. Some folks create self-evolving musical compositions
that require nobody to play
by wiring up complex racks
of blinking hardware, others
craft interestingly modulated
space-noises or clinically obese beats, the likes of which are
normally found only within
the minds of deeply disturbed psychedelic warlords, long
since disappeared into smoke.
Basically, various bits, or modules, are patched together
with wires, so perhaps an
oscillator is wired so that the flat amplitude of a basic
waveform is modulated into an
envelope, filtered to round out the sound, and triggered on
receipt of a pulse from an
expensive bit of kit called a sequencer.
A sequencer is a thing that triggers pulses in sequence,
each of which can be used to
play a note. A note who's pitch is controlled by a twiddly
knob. Put a bunch of notes in
sequence, and there you go, you're Mozart, tunes and
stardom await.
A cheaper version of a sequencer can be created using a
thing called a Clock Divider -
basically, you send in a clock signal, a series of ticks, and
the divider will send out a
pulse on say every 1, 2, 4, 8 and 16 steps each pulse
generated on a different output.
Plug in voices on say 1 and 4 - and you've got the basis of a
simple 4:4 rhythm. Normally
each voice has its pitch set - but comes at a price - and you
don't want to have to set
up multiple voices just to supply different pitches - some
tunes can have up to 16
individual notes (ask Mozart) which in module terms would
very rapidly break the bank.
So here is an idea for a modular synth module, designed to
generate a song's worth of
pitches (or at least pitch-control voltages) that could be
patched into a single voice and
triggered by a simple Clock Divider to create simple but
cheap beats.
The module consists of the following inputs: CV In, and
outputs 0, 1, 2, 3, 4, 5, 6, 7.
Additional controls include: A fine-tune pot, a {flat,
regular, sharp} 3-position switch,
and a {regular, 5th, 7th} 3-position switch. Optional extras
for the delux version might
include individual off-key modifier switches {flat, reg,
sharp} for each output - but let's
concentrate on the basic version for now.
So a control voltage goes in, and populates the outputs with
chromatically pleasant
output voltages according to the scale switches which
define the musical key being
generated. Each output 0 through 7 (or whatever number is
deemed appropriate) can
then be used as the pitch-control for a subsequent
envelope/modulation thing.
Another way to think of it might be as a temporally parallel
arpeggiator.
Appropriate elevator music
https://www.youtube...watch?v=YP_XG08JHyw
[FlyingToaster, Oct 29 2015]
A recent project of mine
http://mitxela.com/...everse_oscilloscope
[mitxela, Oct 30 2015]
A basic mock-up
https://s3-eu-west-...ber/chordsource.png
Here we see the most basic configuration - basically, you set your starting frequency with the pot, dial in the key variables (major, minor, 5th, seventh etc) and calibrated output voltages are generated over ports 1-8 [zen_tom, Oct 30 2015]
[link]
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will it fill in the holes in my road> |
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I'd like the 2 people who bunned this to explain what the hell it is. |
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It sounds like you're going at something totally sideways, which I'm normally all in favour of when I understand it. |
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And here's a little something while you wait <link> |
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You're talking about a modular analog sequencer with an insert point, bypassing internal/external clock or stepper, for direct playing of slots ? (even perhaps, output an average of 2 slots if the input voltage is between the voltage stepping) |
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Synthesizer technology of some kind... |
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I know a bit about modular synths, but nada about their sequencers. |
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The CV in, would that be to shift the whole sequence to a different key? |
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One of the best bits about control voltages in synthesizers is that they're logarithmic (usually one volt per octave), so if you take twelve identical resistors and place them in a line between a one-volt source and ground, you'll get an equally tempered chromatic scale on each of the connections. If you strung the resistors between your (buffered) incoming CV signal and a summing amplifier fed by the CV and a one-volt source, the whole octave would track the incoming pitch. Then just feed them all into your sequencer. |
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Switching in different resistors should be able to sharpen / flatten individual notes. |
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Did he just invent the DCO ? |
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sorry [zt] I can't seem to parse what you're going on about. |
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I'm pretty sure DCO's count ticks for oscillator timing. |
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Great comments guys, I think it's going to be easier to explain by taking
concepts each of you has identified and tying them all together. |
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[mitxela] yes, the CV in would allow for modulation of the key whose
default value would be dialled in via the pot. Plus, loving the fact that
you're already considering the circuitry! |
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[Ian] yes, I'm thinking of a polyphony generator, whose default is set by
pot/cv adjustable source, and whose intervals are defined by the
combination of two 3-position switches whose purpose is to pick
different sets of locations from (I suppose) 16 possible semi-tones. I
think I might need to change the initial 3-position switch from {flat,
regular, sharp} to perhaps {Octave, Major and Minor} with the second
one identifying sub-types of those three, resulting in a combination of 9
different pattern-sets. |
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Each of the voltage outputs would be constant, so we would expect to
feed them into one or more oscillators as a tuning signal. An alternative
might be to feed them into some kind of multiplexer, controlled
perhaps by a Clock Divider signal. Gate and/or envelope would be
triggered by a copy of the Clock Divider signal (or piped through the
associated multiplexer) The multiplexer part is probably an idea for
another day though! The main application I have in mind here is to
create a relatively cheap sequencer alternative. In terms of the tonality
component, I can't help feeling that something like this must already
exist, but I've not found it yet. The simplest application would be to
perform chord/chorus via driving multiple VCOs. |
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[Ian]'s idea of changing the scale dynamically, I like. Either by
optionally feeding some gate inputs (3 of these would give us 8 options,
which might be enough, and 4 gives us 16, which may be too many) or
replacing the pair of switches with an array of options, and using a
trigger signal (and manual toggle button) to step through each of the
possible options. |
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I'm not sure I'm entirely ready for microtonality, I was thinking for
special non-standard scales, we could add a 3-pos switch for each
output, allowing adjustments for each output by semi-tones up or
down. |
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I'm going to try and draw up how the plate might look, and maybe a
possible patch arrangement to put it into context. |
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You may be interested in an electronics / synthesizer project I made recently. A few months ago I started playing with a chip called an ATtiny85, which costs 90p, and I wrote a square wave midi synthesizer for it. It's basically a midi-controlled-oscillator. It has an arpeggiator, pitch bend and modulation, and is small enough to be powered by the midi signal itself. |
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I used this midi-controlled-oscillator, combined with a ripple counter and a multiplexer, to build a very low resolution midi-controlled arbitrary waveform synth (link). It's great fun. It has many similarities to a sequencer. The whole thing cost maybe £5 in total. |
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CV comes in one side,
it's split up and goes to the different pots,
the pots attenuate the voltage,
each pot sends out a CV.... all lower than the original which sucks. |
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So add a global offset voltage at the input stage, equivalent to half the pot attenuation, so you can get outputs higher or lower instead of just lower. Or futz around with 8ve switches |
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And since the sequencer already has all those pretty pots, just sitting there doing nothing, and the only cosmetic change is giving individual outs to each stage... |
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(ya know at some point in time I really was capable of reading something and comprehending it, honest) |
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Or do you mean a modular chorder, with enough twiddly bits that you can get perfect harmonic tuning (or other) out of it. |
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<and again, noticing "clock divider"> |
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So the input CV is going to be (equivalent to) the fundamental of the output chord. A VCO which is controlled by the CV runs at a high enough frequency that it can be clock-divided down into all the partials, perfectly. These pulses are either used to run DCO's directly'ish or reverse-engineered into new CV's for VCO's and other nefarious purposes. |
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Like a one-note Hammond with a variable speed tone-generator motor. |
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Cool. Why didn't you say so ? |
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I still think there's a divider in there somewhere.
Okay... if you want drawbar harmonics then you have
16 - divide the input CV by 2
8 - fundamental - the original voltage.
5 2/3 - multiply by 3 divide by 4 (or something like that)
4 - multiply by 2
et cetera. |
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So no clock, just multipliers and dividers (no idea how that's accomplished, electronically) |
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I've put together (a nice brushed-steel) diagram in the
links above. This unit really is about setting a reference
voltage, and flicking some switches to get a series of
tonally appropriate outputs. The basic version in the link
is the static-interval version, though it does allow the
starting pitch to be varied (modulated) via CV input. |
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The Clock Divider part is just me giving some context as
to how/when you might use this module, setting the
trigger of the divider to control when one or more
voltages from this unit to pass to one or more voices -
that's probably a more complex bit - the idea here is just
to generate a pleasant set of voltages. |
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[edit] it's worth mentioning the links from others - the "Elevator Music" one
from [FT] it seems I've watched before (enough to like it on YouTube
anyway) and yes, it is quite proper. I've another couple of favorites on there
somewhere which I might try and link in a bit. And I really like the Scalegen
demo there, particularly the new-composition from old scale
transformation, that's quite unique. And [mitxela]'s projects never cease to
astound and amaze - I love the artistry, and honest write-ups, but can never
get to the end before thinking "there must be money in this!" - and I'm quite
sure there is. Particularly in the modular-component industry - run a few
funky demos out there on YouTube and hook into some 8-bit, Moog, or other
active fetish being talked about out there at the moment (be prepared to
put in some soldering hours) and there's a few thousand to be made. I will
solder for food if necessary (assuming you're not too bothered about
messy/ugly joins!) |
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I put a perfectly pitched bun into your machine and got 8 harmonically resonant 1/16th buns out. [+] |
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Very nice, I watched one of the first ones where you demonstrate the tap-on/tap-off behaviour when the attack is set to zero, and thinking it was behaving quite "digitally". |
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These oscillator chips seem to have fanbases all of their own - I've seen multiple SID-chip (the SID was the sound chip from the Commodore 64) creations that generate a very distinctive sound indeed, and somewhere on teh intarwebs, I've seen a video someone's made of an electric bass-guitar whose pickups feed into one or more SID chips to create a stringed 8-bit bass-synth. |
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