Logic Noise

Logic Noise

Hacking Music out of Digital Chaos

Elliot Williams


Today's Menu

  • 4000-series CMOS Logic ICs

  • Some Analog

  • Demos Galore and some Circuit Diagrams

  • (Musical Philosophy)

What is Music?

  • Bunch of notes...

  • that you expect,

  • but not too much.

  • Rhythm and Repetition

  • But also variety!


  • Does this have anything to do with CMOS ICs?

  • Tricks up my sleeve

  • Melody Generator ++

  • First sounds, then rhythm, then structure

Tone, Pitch, and Dynamics

Oscillator: 40106

  • Capacitor and resistor determine the pitch


Diode Sync

More Timbre

  • 4070 XOR Cowbell / Cymbals

Pitch: Analog

Pitch: Digital

  • Octaves, divide by 2:
    Binary counters

  • Divide by N:
    4017 decade counter w/ reset

  • 4051 mux again:
    8 oscillators enter, only one leaves

Dynamics: Digital

Dynamics: Analog


Booomm-Tss: 4040 Binary counter

  • Rhythm is just pitch, slowed waaaaay down

  • Whole note, half note, quarter note, eighth note...

  • Four on the floor

Fixing the 4040

  • Invert outputs you care about

  • But keep the non-inverted too: backbeats

Rhythmic Shortcuts: 4089

  • 4089 "rate multiplier" chip is beats in a box

One Pulse per Step: The Mighty 4017

  • Puts out one of up to ten outputs per clock
  • Use pulses to trigger arbitrarily timed events

It don't mean a thing...

  • 4017 + 4040 = regular, off-grid time

All Together

Melody Generator ++

  • Melody generator

  • 4017 makes pitches by division

  • One of eight outputs to reset through 4051 mux

  • Three digital lines into 4051 pick "note"

  • My twist: add some octaves with a 4040,
    drive with SR

Melody Generator ++

Melody Generator ++

  • Control pitch / octave through
    paired clock and data lines

  • Inject sequence into 4-bit shift registers

  • Feed clock / data with detuned oscillators

  • Tweak until "just right"

What Else?

  • Tremendous room for playing around

  • Incorporate microcontroller, FPGA

  • Build standalone instruments

  • Priority encoders, shift registers, complex logic

  • Turn away from "music", embrace noise.

The End

Fittingly Offbeat References