Gravity Engine is a MIDI harmony tool I am building to transform simple musical patterns into evolving chord movement.
In this demo setup inside Reaper, I am using basic repeating patterns across piano, guitar, cello, drums, bass, and violin. Most of the source material is intentionally simple and written as if centered around a C chord. The point is to show how much harmonic movement Gravity Engine can generate from minimal input.
Chord Tokens and Voice Leading
At the center of Gravity Engine is a chord map made of interactive chord tokens.
Rotating around a single token clockwise moves through higher inversions of the same chord.
Moving between tokens chooses the smallest possible voice movement, helping transitions feel musical and connected.
Trigger speed affects velocity, so faster gestures create louder output and slower gestures produce softer dynamics.
The gray notes in the interface represent the stream: the incoming pattern being transformed.
Center Chord Behavior
The center chord behaves differently from surrounding tokens.
Each corner is tied to an individual voice, so moving around it can shift single notes rather than swapping full chord shapes. This makes it possible to nudge harmony with very fine control, including moving multiple voices at once.
Mouse or Keyboard Input
Chord input is not limited to mouse interaction. A connected keyboard can drive the map directly.
With Field Select Mode, single-note input can be used to select chord shapes that would otherwise require multi-note playing. This makes live exploration faster, with gesture-based access to additional variations and inversions, including double-tap and triple-tap behaviors.
Guide Maps and Suggested Progressions
Guide maps include richer harmonic layouts, such as suggested chord chains and color tones, for example add9 variants or secondary-dominant style movement.
In the demo, one short chain moves through G minor add9, F add9, and F major.
The interface also displays full chord labels for each corner, for example F, F/A, and F/C, making harmonic intent easy to track while performing.
GE Link: Leader and Follower Instances
Multiple Gravity Engine instances can be linked with GE Link.
One instance acts as the leader, in this demo the acoustic guitar, while others follow the harmonic decisions. This allows different instruments to stay coordinated while each instance can still apply its own processing behavior.
Magnets: Controlled Pitch Attraction
A feature called Magnets adds another layer of melodic control.
A heat zone attracts output notes toward a target range, which can move over time. In practice, this means a very simple repeating note stream can be reshaped into something with harmonic movement, octave contour, and evolving melodic direction.
The violin example in the demo shows this clearly: a basic repeating input gets transformed into a more expressive and dynamic line.
Why This Matters
Gravity Engine is designed to turn minimal MIDI material into harmonically rich output while preserving playability and musical flow. The combination of chord tokens, voice-leading logic, instance linking, and magnet-based attraction creates a workflow that is both structured and exploratory.