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invention

16-Step Sequencer

by renaudbedard

Published on May 8, 2017

Plays 16 distinct notes in sequence without overlapping, by triggering 4 micro-sequencers in alternating order.

Based on the original 8-step sequencer here : https://littlebits.cc/projects/8-step-sequencer

 

Duration: 15 minutes

How To Make It

STEP 1 : Clock portion

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Use a pulse module to drive the clock of the sequence. Use a latch to "smooth" the output, which ensures that 50% of the time is spent either in off or on state; not using a latch results in a swing-like tempo that feels a bit off. The latch should then connect to some kind of splitter (I used a branch) which feeds into the twin 8-step sequencers. A branch is useful because the 3rd output can be used to trigger one of the envelopes. One of the two main branches should have an inverter, and both should then run through a latch to make them run at half-time. Note : If you have an extra oscillator on-hand, you can obviously use it instead of a pulse module to drive the clock. Otherwise, you can use a filter module set to self-oscillation (maximum peak) and to its lowest cutoff point to simulate a fast oscillator; you might have to latch it a couple times to slow it down.

STEP 2 : Sequencer portion

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Build two 8-step sequencer based on the same design. The main difference is that one of them is fed by an inverted signal from the main clock. Both should be latched. I used forks to split the two micro-oscillators of each 8-step, which is a bit wasteful because I only need 2 signal paths; you could use splits instead. All micro-sequencers feed into an oscillator, which feed into an envelope (optional) and then mix down to the speaker via a filter & delay (optional). The really tricky part is to make it sound musical... programming 16 steps with 4 different oscillators without any kind of scale quantization is hard. I suggest going one micro-sequencer at a time. You might ask yourself, why use 4 oscillators? Why not use 2 or even 1, and downmix the signals from the micro-sequencers instead? But it turns out that mixing down control signals makes them interpolate from one to the other, kind of like portamento, which is a cool effect but not the one I was going for. So if you want clear separation between notes, you'll have to go with 4 discrete oscillators.

STEP 3 : Envelopes

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Like the original 8-step sequencer design, envelopes need to be triggered manually because they don't react to the lack of silence between impulses. This could be remedied by using 4 envelopes (1 per oscillator) but it's possible to use only 2. The idea is to feed the envelopes the signal you feed to your 8-step sequencer portion before it gets latched.

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