DIY random looping sequencer in Eurorack format
Size: 10 HP
Size: 10 HP
21 things to know about the Turing Machine
- This is a binary sequencer, based around a 16 bit memory circuit called a shift register. It’s designed as 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: This Random Looping Sequencer is a module that produces clocked randomly changing control voltages. Unlike many random voltage generators, these sequences can be locked into loops that repeat according to the length control.
- Despite being hard to explain, since it was launched in June 2012, the Turing Machine has become one of the most popular Eurorack DIY projects. The #turingmachine tag on Instagram contains lots of great demos (and a certain amount of the real Alan Turing).
- Turing Machine Expanders connect to the back of the module, and take the sequence from the main module and use it in different ways:
- 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.
- The original demo video (using the old Mk1 module) is probably the easiest way to understand the concept of a locking and slipping sequencer:
- While this 27 minute video from DivKid explains everything you need to know about the Turing Machine and expanders:
- You can try out a fully operational Turing Machine + Pulses + Volts in the free VCV Rack software.
- 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.
- Like most sequencers, you can also use the Turing Machine like an oscillator - or more accurately a waveshaper. When clocked at audio rates by a square wave oscillator, it creates random wavetables. This video explains:
- 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.
- The original design had a backpack PCB to power the expanders. The update in 2016 added a new panel design plus:
- Rotary loop length switch
- Pulse out
- Two boards, includes Backpack circuit to drive expanders (compatible with old Music Thing expanders)
- Easier to build: a larger PCB in the same width, clock and noise circuits are more robust
- Noise level trimmer & reduced voltage in noise circuit to make circuit more robust with different noise transistors
- Turing Machine is open source, which has inspired many offshoots, alternative panels and third party expanders, including:
- Read more about Music Thing Modular and open source.
- 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 computer scientists find it very annoying.
- 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 as a first build). 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.
- Once you've built the module, don't forget to calibrate it to ensure it locks properly.