This video introduces the Random Looping Sequencer ‘STRACHEY’.
The module is named for computer pioneer Christopher Strachey.
Biographical information can be found at:
https://en.wikipedia.org/wiki/Christopher_Strachey
https://history.computer.org/pioneers/strachey.html
Details of Stracheys’ involvement in the first recording of computer-generated music can be found at:
https://link.springer.com/chapter/10.1007/978-3-319-53280-6_8
https://blogs.bl.uk/sound-and-vision/2016/09/restoring-the-first-recording-of-computer-music.html
Full design details for the STRACHEY Sequencer are at:
https://github.com/m0xpd/STRACHEY
and the Tuning Strategy which is central to STRACHEY’s operation, is at:
https://github.com/m0xpd/TuningStrategyForVoltages
STRACHEY’s architecture is inspired by Music Thing Modular’s ‘Turing Machine’ and its ‘Voltages’ expander. STRACHEY implements a software version of a Turing Machine and TWO VOLTAGES expanders, which it tunes according to my “Tuning Strategy’. The two virtual Voltages expanders produce outputs for STRACHEY’s channels A and B.
Even though they are both set to the same initial tuning, channel A and B’s outputs are different because:
1) Channel A appears at every beat of the system clock, whereas Channel B only appears at the onsets of a Euclidean Pattern of length equal to the Turing Machine’s cycle length and density set by STRACHEY’s DENSITY controls. A CV input allows the density to be modulated to provide change and interest to this parameter.
2) Channel A’s pitch range can be extended by up to 3 octave using the SPAN controls. Again, SPAN can be CV controlled.
3) STRACHEY implements a ‘Permutation matrix’ between the gates and weights of channel A, which can change dynamically according to 16 different ‘METHODS’, thereby introducing a new dimension of variation to Random Looping Sequencers. Like all STRACHEY’s functions, this permutation is under CV control.
This is my new module a random looping sequencer which I’ve named for Christopher Roi a pioneering computer scientist who went up to Cambridge in 1935 where he met Alan churing a name you’ll be familiar with Christopher went on to do all sorts of interesting things in his life and career not least
Working on the development of the Computing language CPL which was a precursor of C which is involved in the language which is running on the the controller inside this sequencer which is a nice circular story but perhaps the most important link to electronic music is the fact that
Christopher worked on Alan churing Mark 1 and Mark I computers here in Manchester and coded them to play music he was one of the first people in the world to do so to code computers to play music he was certainly the first person in England to do that and his
Work led to the world’s first recording of computer generated music I’ll put some links below this video to allow you to chase up that story and to hear those recordings I’ve spoken about Alan churing well the left hand side of the front panel of this module is an
Implementation of the touring machine a familiar and rightly famous Euro module from music thing modular the line of LEDs on stry is a direct copy of the line of LEDs on the touring machine and this big conspicuous control on the touring machine is this control here the first
Of the major controls on the stroy sequencer which I’ve named touring because I thought that was the best name for it it doesn’t have a name on the touring machine but I’ve called it touring for those of you not familiar with the touring machine it generates a
Gate sequence which can be randomized or held uh as a repeating sequence and is a variable length set by a length control and that gate gate sequence drives uh the weights of a sequencer ordinarily in the touring machine well well I should first say that there is an analog output comes
From the touring machine which is reproduced here down at the bottom right it’s bottom right on the touring machine as well but ordinarily you might connect the those gates to an expander module of of this kind music modular voltages module in which case you set up weights on these
Sliders in order to make some interesting outputs as a consequence of these Gates being excited inside stry there is effectively an emulation of the voltages expander but of course you don’t see the sliders because I’ve programmed settings of the sliders in what I’ve called tunings selected by this second
Control and so for any gate pattern and tuning we get outputs on the main output Channel which I call Channel a we can listen to that now so we’ll take a voltage per opave see V output from Channel a and an Associated trigger output for channel a and listen to the
Consequence it’s in a tuning which corresponds to an arpeggiation of a minor 7 chord you here there are just three notes being sounded at the moment which constitute the root the fifth and the minor 3D adding up to that at the moment Just A Minor triad if I allow
This gate sequence to get more complicated rather than the fixed pattern you’re hearing repeated we can add in the flattened seven those are all of the notes you’re going to hear in this tuning however as I suggested earlier there is not just one tuning but a whole
Bunch of them in fact there are 24 and you can move between them uniquely in this sequencer that’s to say you can’t do it with the voltages expander because you’d have to carefully set all of those sliders but in this machine you can just select with this control or with um CV
Inputs which control this um knob as well immediately between different tuning so you’re hearing at the moment the arpeggiated Minor 7 we can go straight to a major seven which is adjacent to it in these tunings and I happen to know that next to that is a diminished cord and that’s those
Changes are all with the same gate pan which of course we could open up to be slightly more random or variable so you’re getting there a feel for what this stretchy sequencer is all about the next aspect of the stretchy sequencer I’d like to show you takes the
Arpeggiated chords or scales or modes or whatever have been derived from the basic tunings such as the Minor 7 pattern that we saw a moment ago and develops it by adding to the pitch span that the arpeggiation covers it does that with the span control and CV input as well associated
With them allows you to add in up to three octaves of pitch range extension sounds like [Laughter] This I did all that with a fixed pattern but if you allow the pattern to Change Okay you’ve seen the activity on channel a and you’ve seen the opave extensions through the span control now it’s time to look at what happens on channel B Channel B produces notes derived by the same gate sequence and the same weights the same tuning as Channel
A however there is a difference in the onsets of those notes and that is related to this third major control the density control as I’ll demonstrate now first of all take the pitch CV output for channel B and the trigger output for channel B if I can keep hold of the cable
You hear that the onsets are less frequent I can turn them all the way down to be off as I increase density with this Potentiometer they get more and more frequent until they sound on every clock cycle but in the middle there’s a ukian pattern generator which generates a ukian pattern of length determined by the touring machine’s repeat length and density set by this density control and of course there is a CV input as well
Which collaborates with that uh potentiometer to control the density so importantly you can modulate the density with the CV input and make things change and as the pattern changes then of course the um the pattern that you’re hearing changes and the density follows that on both channels A and
B you get this sort of Effect the final major ingredient in stretching is associated with the method and change Controls which allow you to permute the order of the weights that’s to say change the order of the weights it’s equival equalent to having a setting on the voltages expander and then being able to instantaneously change the order in which these slider settings are made so you’ve got here a
Few full over to the right which you instantaneously swap over onto the other sliders some of which are in intermediate settings they keep the precise settings of those sliders but move them on to other sliders something you clearly can’t do on a physical voltages device but you can do on this sort of
Implementation it’s got various ways in which it can permute and swap around the weights and those different ways are called different methods the method associated with having all of these LEDs illuminated which describe the different methods is a shuffle where it just randomly shuffles the order you can hear I’ve got the minus
7th uh tuning um set up again because you become familiar with it in this video it’s just got two nonzero weights which are sounded as this single active GATE scans through you can hear those two notes apart from the root note Fifth and minor 3D if I activate this Shuffle they will
Change in their position in the sequence I’ll do it now they’ve gone right to the end of the sequence now instead of where they were in the middle I’ll do it again they’ve gone further back and the minor thir is now right at the beginning of the sequence I’ll do it
Again they changed in order now it’s going minor 3rd Fifth and they’re kind of roughly where they started in terms of position in the eight notes done it again there you see that the method indicator flashes after you’ve requested a change because the change isn’t made until the end of the
Eight in this case eight um beat sequence if you’re on a different length then it changes at the end of that length one more call on that conversely method zero is to reset to where it started with the in this case uh tuning for the arpeggiated minor
7th this idea actually came from an analogy with bell ringing um bell ringing by by both methods and changes I’m not a bell ringer but I’m kind of interested in and appreciate the mathematics behind it there is to demonstrate this another tuning which has a descending major scale which is typical
Of the way in which bells are tuned if there are eight bells in a bell tower and another one of the methods which is number six if I were to continually invoke that by either continually pressing change or using an external input to continually assert it
That’s to say call it every time we look through the eight beats you get a bell ringing method which is it’s called plane hunt I’ll demonstrate that to you [Laughter] [Laughter] Now you heard it back go back there to a sending scale [Laughter] again and now it’s in an ascending scale this is obviously of no real interest in um ordinary synthesizer applications what it’s demonstrating is the ability to Jumble up the weights According to some predictable process now if you
Listen to the another tuning go back maybe to that minor third and minor 7th sorry tuning that we had before and then get a slightly more complicated weight pattern than just the single gate scan something like that here I’m going to just let this sound as a repeated pattern so no
Variation with the gates but instead we’ll just have the bell ringing method of plain hunt going on and you’ll hear variation all of a sudden coming into this sound through nothing other than the application of this very old algorithm for permuting [Laughter] bells so what you have here is another way
Obviously that plane Hunt is just one of the in fact there are 12 different ways of permuting the weights implemented in here what another way of introducing some variation apart from the traditional method with the touring machine of of literally generating new weight vectors and and gate vectors rather a
New way of introducing variation into a random looping sequencer by introducing permutation of the weights and changing the way in which the gates couple to the settings the pitch settings of a Sequencer E Oh