Music Making Machines

Notes about making Music Making Machines.

The specific software used is the freely available and open source VCV Rack, and using only its stock modules. The same techniques can be used in any medium that allows basic but direct manipulation of signals (modular hardware, other visual patching softwares, music programming languages etc).

Meta

• Play. Musical instruments take decades to learn how to operate. These techniques are no different.

• Embrace limitations. Limitations delineate the playground we're playing in, allowing us to focus on and get in the flow of playing.

• Keep a patch journal. Writing about music is like dancing about food. Still, there is value in being immersed in what one is doing, and writing is one common way. Not the only way though, there can be other rituals too.

Steps

1. Spend time with the stock modules.

   • Their documentation is great.
   • Here is a quirkier walkthrough.

2. Recreate some patches others have made.

   • TODO

Thoughts

Sequencer

The heart of music making machines is often a sequencer. This is in contrast to if we were doing sound design, where the focus would be on the oscillator or the filter, or if we were making music itself, where the musician would be the sequencer.

Everything can be modulated by a sequencer, including the sequencer itself.

Note

An oscillator can also serve as a sequencer, especially if quantized.

However, one doesn't necessarily have to use clocks or a sequencer. A windchime is a great example of a music making machine that has no clocks. It uses a quantizer to convert the noise signal provided by wind to notes on a musical scale, with the wind also serving as the background noise in which the notes sit.

VCV Rack specifics

Reference: VCV Rack Manual

Here are some more notes you might find useful, and below are two koans: signals are voltages, and patches are text.

All signals are voltages

Any output can be connected to any input; all cables carry (virtual) voltages.

However, purely semantically, there are distinctions:

• Audio signals are audible when played through speakers. They contain audio-rate frequencies typically between 20Hz to 20kHz.

• CV (control voltage) signals modulate parameters of other modules. e.g. an LFO (low frequency oscillator) can oscillate the pitch of a VCO (voltage-controlled oscillator), or the volume level of a VCA (voltage-controlled amplifier).

• 1V/oct (1 volt per octave) signals are control voltages, that is, CV signals, that represent a pitch or a note. In this standard, an increase of 1V increases the pitch by 1 octave. Since there are 12 notes in an octave, an increase in 1/12 V increases the pitch by 1 note.

• Gate signals carry an on/off signal. 0V represents off, and a positive voltage (typically 10V) represents on. For example, a gate signal can turn on when a key is pressed and off when the key is released.

• Trigger signals are short gates, typically 1 millisecond, that cause an event to occur, such as a triggering a sound.

• Clock signals are triggers played at a steady tempo.

Viewed as a tree:

• Audio
• CV
  • 1V/oct
  • Gate
    • Trigger
      • Clock

Tip

Remember that everything is a voltage. (Most) modules are not about "audio" or "CV". It only matters whether a signal is at audio rate when trying to move to a speaker. Before that, at any point, it is only voltages.

Warning

While we just emphasized that everything is a voltage, there is one implementation distinction between "audio" voltages and "CV" voltages. The VCV VCO uses anti-aliasing to avoid introducing harmonics beyond the Nyquist frequency, so the waveforms it generates exhibit the Gibbs effect (i.e. the square waves are not exactly square but wiggle at the edges).

The VCV LFO doesn't use anti-aliasing. Thus, the LFO is more suited for generating CV for modulation, while the VCO is more suitable for generating audible waveforms.

Input and output voltages carried by patch cables are thus in the (virtual) voltage unit, V. Both oscillators and CV generators typically produce 10 Vpp (peak-to-peak) signals, but audio outputs are usually ±5V, while CV sources are either 0 to 10V (unipolar CV. e.g. this is the default for the VCV LFO) or ±5V (bipolar CV; LFO emits this when OFST switch is off).

Pitches and frequencies

Frequency knobs on VCOs typically default to C4 (middle C, MIDI 60, f0 = 261.6256 Hz). This can be offset by an input voltage V which would use the 1 V/oct (volt-per-octave) standard for CV control of frequency information. Thus the offset frequency in terms of the input voltage V would be f = f0 * 2 ^ V, where f0 is the aforementioned baseline C4.

LFOs and clock generators typically default to 120 BPM (f0 = 2 Hz).

Patches are text files

Almost. They're compressed folders containing the patch JSON, alongwith any wav files that the patch uses.

tar xvzf my-patch.vcv
more patch.json

Tip

I know what you're thinking. Since they are JSON files, maybe I can write a program to generate them...