Features
Everything the engine can do.
Guitar chord finder, voicing generator, scale finder, chord progression builder, and more. FretMotion is a music theory engine for guitar, computed from first principles.
The Engine
This is what powers every tool. It's not one feature, it's the foundation that makes everything else possible.
Universal chord parsing
Understands every notation system: jazz symbols (Δ7, ø, -7), tab shorthand (C, Am), slash chords (Am7/E), and complex extensions (9#11, 7b9b13). One parser to rule them all. Over 60 chord types recognized.
Voicing generation
Generates every physically playable voicing for any chord, in any tuning, at any position on the fretboard. Uses recursive search with early pruning on finger span and string coverage. Real finger assignments with barre detection, filtering out shapes no human hand can actually reach.
Voice-leading optimization
Takes any progression and finds the smoothest voicing path: the sequence of chord shapes that minimizes hand movement between changes. Uses dynamic programming on a layered graph of all candidate voicings. The result: your fingers barely move.
Harmonic analysis
Harmonizes any scale to reveal every diatonic chord with Roman numeral analysis. Detects keys from pitch-class sets. Suggests substitutions (diatonic swaps, secondary dominants, tritone subs) and generates full reharmonization alternatives.
Fretboard modeling
Every tuning supported: standard, Drop D, Open G, Open D, DADGAD, half-step down, and extensible. Capo transformations compute instantly. The engine maps any scale or chord across the entire fretboard with interval coloring.
Transposition & capo optimization
Transpose any progression to any key instantly. The engine can find the best capo position so you play simple open shapes while sounding in any key. Perfect for singers and beginners.
Voicing filtering
Filter by type (open, barre, movable, shell), by note count (min/max), by bass note (root-in-bass, slash voicings), by skill level. Stack constraints to get exactly the voicings you want.
Chord diagram rendering
Every voicing comes with a publication-quality chord diagram: SVG-rendered with finger dots, barre indicators, open/muted strings, fret numbers, and note labels. Ready for screen or print.
10+ Powerful Tools. One Subscription.
Every tool is a different lens on the same engine.
Fifth Circle
Interactive circle of fifths for guitar.
Spin the interactive circle of fifths. Tap any chord to hear it, see its guitar voicing, and check whether it belongs to the current key. Build progressions visually.
Chord X-Ray
Guitar chord finder. Look up any chord, see every voicing.
Type any chord symbol and get all playable voicings with chord charts, fingerings, and type classification. Reverse lookup too: enter fret positions and identify the chord.
Song Workshop
The smoothest path through any progression.
Paste a chord progression and the engine optimizes the entire voicing path for minimal hand movement. Transpose, find best capo, filter by style, all in real time.
Harmony Lab
Every chord that fits a key.
Pick a key and scale. See every diatonic chord with Roman numeral analysis and voicings. Works for all 7 modes, harmonic/melodic minor, pentatonic, blues, and more.
Fretboard Map
Guitar scale finder. The whole neck, visualized.
See any scale or chord mapped across all strings and frets, color-coded by interval. Root notes highlighted. Works with every tuning.
Practice Builder
Learn guitar chords. Targeted drills for your weak spots.
Enter chords you know. The engine finds your hardest transitions, builds practice drills from easy to hard, and suggests the best next chord to learn based on proximity to what you already play.
What Key Is This?
Instant key detection.
Paste any chord progression and get the most likely key matches ranked by score. Works with any combination of chords, even chromatic or ambiguous ones.
Singer Adapter
Any song, any key, playable.
Transpose to your singer's key, find the best capo position for easy shapes, and get optimized voicings, all in one step.
Chord Simplifier
Easy guitar chords from complex symbols.
See the full voicing, a 3-note shell, and the underlying triad side by side. Pick the version that matches your skill level.
Style Converter
Same song, different vibe.
Re-voice any progression as jazz shell voicings, open folk shapes, or minimal 3-note voicings. The engine re-filters and re-optimizes the entire path for each style.
Reharmonizer
Chord substitution guide. Surprise yourself.
Get creative substitutions for every chord in a progression. Diatonic swaps, secondary dominants, tritone substitutions, each with voicings and diagrams.
Style Explorer
Compare every style at once.
See the same progression voiced as jazz shells, folk open chords, rock barre, power chords, and minimal shapes, side by side. Sorted by total hand movement so you can pick the smoothest fit.
Progression Generator
Chord progression generator. Genre-aware, instantly.
Choose a key, scale, and genre. The engine picks a template, builds diatonic chords, and finds optimized voicings. Click any chord to enrich, simplify, or substitute it in place.
Structured computation.
Typical tools
- Inconsistent results
- Limited chord vocabulary
- Rate-limited, credit-based, slow
- No real understanding of theory
- Can't guarantee playability
FretMotion
- Deterministic: same input, same answer
- 60+ chord types, every voicing computed
- Instant, no rate limits, no credits
- Built from first principles
- Every voicing verified as physically playable
Ready to explore?
All features. All tools. One price.