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Music Thing Modular Turing Machine MkII

Eurorack Module By Stephan Whitlan
Published January 2018

Size: 10HP. Current: +12V = 40mA, -12V = 0mA.Size: 10HP. Current: +12V = 40mA, -12V = 0mA.

If we wind time back to those heady days of the ’60s, we find two schools of thought on what a modular synthesizer should do (and how it might do it). These days we call these the East Coast and West Coast schools, as exemplified by Moog (East) and Buchla (West). Sonic differences apart, the defining modules might be in Moog’s case the 960 step sequencer, and for Buchla the Source Of Uncertainty. These more or less define the two approaches, further polarised by the adoption of the standard keyboard by one manufacturer, and a deliberate rejection by the other. History will go on to justify the commercial sense in one decision over the other — not that Buchla didn’t make some money, nor that his systems were not revered. I think this meant that working musicians usually preferred a ‘scientific’ repeatability rather than serendipitous chaos.

Despite my distinct East Coast leanings, I am not adverse to a bit of random now and again, and have already reached beyond Sample & Hold (and its cousin Trigger & Hold) with a Doepfer A-149 Source Of Uncertainty. In parallel with my step sequencers this ensures sufficient variations in otherwise static patches. The thing to note is that you need both sequential surety and a bit of chaos; what if you could get them all in one module? Enter the Turing Machine from Music Thing Modular.

Actually the unit I have in front of me now is the updated MkII along with the new Pulses and Volts expanders. These are slightly tweaked versions of the originals (which had black fascias), and are available as kits to those brave enough — of which more later. Hand on heart, I can’t find you a precise justification for using the term Turing Machine — beside that its behaviour is somewhat enigmatic (sorry) — but it is clearly a module that seems to have a mind of its own. It also amused me (eventually) that ‘how to work it’ instructions seem non-existent; thankfully a very helpful YouTube video takes you through the basics, but why should it really matter that you need to know what the unit is doing, or how you might affect its output, if it’s purpose is to produce uncertainty?

The key control on the main panel is a large friendly black knob with no markings of any kind, barring the abstract panel graphic behind it. All you need to know is that in the 12 o’clock position the on-board shift register generates a stream of random voltages, in sync with the clock pulse presented at the Clock (in) socket, and, depending on the number of steps set by the Length switch (2, 3, 4, 5, 6, 8 ,12, 16) present at the output jack, something like a random looping sequence. You can ‘lock’ this sequence by rotating the knob all the way clockwise (five o’clock) if you hear something you particularly like, and are quick-witted enough! So far so good, but the real magic occurs when you now reduce the knob position into the four o’clock to one o’clock zone. Now the sequence will start to ‘slip’ as some of the sequence notes are replaced, one by one, with new data from the register. This slip occurs faster as you move from three o’clock to 12, at which point the register is again constantly refreshing. For ‘on the fly’ reset, the Write switch when depressed injects a ‘zero’, which might be a better label, or even ‘clear’.

If you are going to use this data melodically then the Scale knob sets the output range, from nothing to several octaves (5V I guess), though you will need a Quantizer in line for full-on Western 12-tone work. So what happens if you turn the big knob to the left, I hear you ask? I wasn’t sure either! It seems that at fully anti-clockwise (seven o’clock) you get ‘lock’ again, but it will double the length of the sequence: five on the switch becomes 10 ‘notes’. Time spent getting used to manipulating the knob will soon give you confidence that you are achieving a kind of control over proceedings, though I was never completely certain! And if you fancy conceding to chaos, then a CV input allows external control of the big knob. Wild! Rounding out the panel is a ‘noise’ out jack which, er, outputs noise, and a ‘pulses’ output that presents a rhythmic pattern in sync with the sequencer clock which appears to only ‘go high’ for register steps over 1.5V. The result is a locked cyclic pattern of triggers which will also mutate with the ‘notes’, the combination of which kept me amused for hours.

The Volts expander panel just has five pots and an output socket and acts like a mini-sequencer. Except that the pots ‘trim’ voltages supplied from the register and will vary with both knob settings and the sequence length switch, though they stay locked in time. Uses for this might be filter cutoff CV or maybe a second harmony line. Either way its five-step cycle (non-negotiable) will ensure polyrhythmic interest/mayhem! The icing on the cake is the Pulses expander. This has seven steps, locked again to the main Turing Machine cycles with trigger output for each step (1-7) and also OR outputs for when multiple steps are ‘high’: 1&2, 2&4, 4&7, and lastly 1&2&4&7. Send these to trigger percussion voices and the like...

I mentioned earlier that these modules are available to buy as kits, and I had much fun re-connecting with my inner 10-year-old as I wielded my soldering iron in step with the excellent (idiot-proof) instructions. All the components needed are included, though I did struggle a bit with identifying the resistors (is that brown-black-blue or purple-brown-green?), and except for an incident with breaking a leg off a capacitor it took me maybe three hours from start to finish — and it worked first time!

There is little more to say, except that once installed in my system I had a huge amount of fun with these modules, eventually driving three SH101’s and triggering A-155’s and 960’s through four quantisers. Did I manage to make any worthwhile music? Maybe not, but whole days actually disappeared in just exploring the areas between the expected and the random. I don’t think good old Sample & Hold will cut it any more. The Turing Machine and its expanders are excellent modules — justly popular as kits — which may just have moved me closer to the West Coast.

Turing Machine MkII Kit £106.69, Volts Kit £40.98, Pulses Kit £42.90. Prices include VAT.