Terrarum Locus
MIDI Generator
Locus app icon

Locus

An AUv3 MIDI generator for iOS — a locked-loop mutator that creates evolving one-bar loops without losing their identity. Freeze a loop with Variation at 0, or shape its evolution with separate controls for drift, mutation frequency, and severity.

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See Locus in Action

Quick Start

  1. Open your Audio Unit host (AUM, Drambo, Logic Pro).
  2. Add Locus as an AUv3 MIDI effect or MIDI generator.
  3. Route Locus MIDI output to a synth on another track.
  4. Choose an archetype and press Create.
  5. Set Variation, Rate, and Strength to shape how far, how often, and how strongly the loop evolves.
Note: Locus outputs MIDI only. It will not make sound until routed to a synth.

What Makes Locus Different

Frozen loops
Variation at 0 never changes — a stable foundation to build tracks on
Evolving loops
Variation limits drift, Rate sets mutation frequency, and Strength sets mutation severity
Deterministic
Same settings always produce the same output
RT-safe
Real-time-safe audio thread — zero glitches under load

Evolution Controls

Evolution is evaluated at bar boundaries. Each control has a separate job, so you can tune the amount, timing, and character of change independently.

Variation
Limits how far the pattern may drift from the original motif. 0 is the master freeze; higher values permit more cumulative change.
Rate
Sets the probability of requesting a mutation at each bar. 0 never requests one, 127 requests one every bar, and intermediate values produce irregular gaps.
Strength
Sets the severity of each mutation. 0 still allows a single subtle edit; higher values permit larger structural changes and more micro-edits.
Activity rings
The inner rings inside Rate and Strength light for bars where Locus accepts a mutation. Near the Variation limit, Locus may make a smaller bounded edit to keep evolving.
Try this: For subtle evolution averaging about once every eight bars, use low-to-moderate Variation, Rate near 16, and low Strength. Timing will vary around that average.

The 13 Archetypes

Each archetype gives Locus a distinct musical personality to start from.

  • Puncture — sharp, accented pointillism
  • Groove — swung, feel-forward motion
  • Pulse — steady, driving repetition
  • Cascade — rolling, descending runs
  • Thump — weighty, low-centered hits
  • Cluster — dense, compact groupings
  • Chaos — unpredictable, scattered energy
  • Even Pulse — grid-aligned even spacing
  • Interlock — two-part hocketing patterns
  • Call/Answer — conversational phrasing
  • Arc — rising and falling shapes
  • Wander — meandering, free motion
  • Sparse Fractal — self-similar space

Usage Notes

Plugin type
MIDI only (no audio output)
Best hosts
AUM, Drambo, Logic Pro, GarageBand
Grid
One-bar motifs on a fixed 16-step grid
Transport
Syncs to the host clock at bar boundaries

Common Questions

  • No sound: Locus outputs MIDI only. Route it to a synth track.
  • The loop changes too much or too often: Set Variation to 0 to freeze it. Otherwise, lower Variation to limit total drift, Rate to request mutations less often, or Strength to make each change subtler.
  • It sounds different each time I load it: Same settings always produce the same output. Check that the archetype, seed, and variation match.
  • Changes feel delayed: Locus applies changes at bar boundaries for clean, glitch-free timing.