17 things to know about Turing Machine

8 HP | 40mm deep | 40mA
Designed 2012 Updated 2016

Modular Grid | Videos
Github | Schematic

Available from Thonk

The Turing Machine makes music for you. It's a binary sequencer, based around a 16 bit memory circuit called a shift register. It’s a sequencer that you can steer in one direction or another, not one that you can program precisely.
You cannot program this sequencer to play specific tunes. You cannot save sequences. You can never go back to a sequence that has changed.
To put it another way: the Turing Machine produces clocked stepped randomly changing control voltages. In other words, melodies, basslines, sequences. Unlike many random voltage generators, these sequences can be locked into loops that repeat according to the length control.
The Turing Machine has become one of the most popular Eurorack DIY projects since June 2012. The #turingmachine tag on Instagram contains lots of great demos (and a certain amount of the real Alan Turing).
This 27 minute video from DivKid explains everything you need to know about the Turing Machine and the expanders.
And here's me talking for 20 minutes about how the Turing machine works and how it was designed.
Here is a nice review of the Turing Machine from Sound on Sound Magazine
Turing Machine Expanders connect to the back of the module, and take the sequence from the main module and use it in different ways:
- Volts adds an extra voltage output, with the sequence set by five pots.
- Pulses turns the sequence into beats: eleven rhythmic pulse-train outputs.
- Voltages adds two CV outputs controlled by 8 faders.
- Vactrol Mix is a sequencer controlled matrix mixer. It's fantastic for rhythmically cutting up audio, stereo panning and feedback loops, but a little hard to explain.
In the Turing Machine, looping is controlled by the big knob.
- At noon, the sequences are random.
- At 5 o'clock, it locks into a repeating sequence.
- At 7 o'clock, it double locks into a repeating sequence twice as long as the 'length' setting.
- At 3 o'clock or 9 o'clock, it slips; looping but occasionally changing notes.
You can try out a fully operational Turing Machine + Pulses + Volts in the free VCV Rack software
Electronically, the circuit was inspired by the long history of shift register pseudorandom synth circuits, including the Triadex Muse, Buchla 266 Source of Uncertainty and Grant Richter's Noisering.
Musically, the module was inspired by 60s and 70s minimalist process music by people like Steve Reich, Terry Riley or Philip Glass: “I am interested in perceptible processes. I want to be able to hear the process happening throughout the music.To facilitate closely detailed listening a musical process should happen extremely gradually.” Steve Reich, Music as a Gradual Process, 1968
While designing the Turing Machine, I compiled this Random Reading List which includes notes on the history of random sequence generators from Marvin Minsky's Muse to Don Buchla's Source of Uncertainty to Doepfer's A-149 module.
Tony Surgeon is a long-time Turing Machine user. In this workshop from 2016 he shows how he uses it to generate sequences which are then looped on an Octatrack.
Turing Machine is open source, which has inspired many offshoots, alternative panels and third party expanders, including:
- Mystic Circuits' Vert and Leaves
- Grayscale Modular's Permutation
- Magpie Modular's crazy combo panels
- Software Turing Machines inside the Ornament & Crime module, Frames Parasites firmware, Reactor Blocks, VCV Rack Modules and even Mutable Instruments' Marbles.
The Turing Machine is not a real Turing Machine the way Alan Turing explained it. The name is vaguely relevant because the module uses a loop of data being changed, but the similarity ends there. It's certainly not a 'probabilistic random sequence generator based on the research of Alan Turing' ;-).
The original Mk1 documentation contains more detail about how the Turing Machine works, including a block diagram.
The Turing Machine is a fairly straightforward through-hole DIY build, but it's fairly dense and takes a while to complete, so probably shouldn't be a first DIY project (I always recommend Mikrophonie or Mini Drive as first builds). Build documents are available from Thonk. If you get stuck, the Github Issue List is probably the best place to start - remember to check closed issues as well as open ones.