Music Theory Companion
Your all-in-one music theory toolbox: scales, chords, ear training, voice leading, and more — for every instrument.
Music Theory Companion is a comprehensive reference and practice tool for musicians at any level. It merges scales, chords, ear training, voice leading, and songwriting support into a single app so you spend less time switching between references and more time making music.
At its core is a library of 86 heptatonic scales and modes, each with its complete set of diatonic triads and seventh chords displayed on a realistic piano keyboard and guitar fretboard simultaneously. A 1000+ chord library shows how any chord is constructed, and the Circle of Fifths visualisation covers all 86 scales in both clockwise and counter-clockwise orientations.
For composers and arrangers, the Cube Dance tool brings Neo-Riemannian voice leading theory into a practical format — helping you navigate smooth harmonic movements between chords that are not strictly diatonic. The built-in pitch detector works with any instrument for scale practice, and interval ear training exercises develop your ability to recognise intervals by ear.
Supporting tools include a configurable metronome, staff notation in treble and bass clef, a musical symbols reference, and links to curated online music theory resources. Whether you are a pianist working through jazz harmony, a guitarist exploring modes, or a songwriter looking for fresh chord progressions, Music Theory Companion gives you the theory and the tools to apply it immediately.
Features
Scale Library (86 Scales and Modes)
86 heptatonic scales and modes, each displayed with all seven diatonic triads and seventh chords on both piano and guitar fretboard. Supports sharp and flat notation, and can be viewed in simplified or advanced note formats.
Chord Library (1000+ Chords)
An extensive chord reference showing chord construction — intervals, note names, and voicings — for over 1000 chord types.
Circle of Fifths
Interactive Circle of Fifths covering all 86 scales in both clockwise and counter-clockwise orientations. Shows diatonic triads and 7th chords at each position.
Voice Leading — Cube Dance Tool
A visual tool based on Neo-Riemannian theory that shows how chords connect through smooth voice leading. Helps identify non-diatonic chord movements that still sound cohesive.
Pitch Detector
Microphone-based pitch detection that identifies the note you are playing or singing and matches it against the selected scale.
Interval Ear Training
Exercises that play intervals for the user to identify by ear, building relative pitch recognition over time.
Realistic Piano Keyboard
An interactive piano keyboard with multiple instrument voices for playing back scales and chords. Supports both treble and bass note display on staff notation.
Guitar Fretboard (Left- and Right-Handed)
A realistic guitar fretboard display that shows scale tones and chord shapes. Supports both left-handed and right-handed layouts.
Metronome
Configurable metronome with multiple sound options.
Staff Notation
Displays notes and scales on treble and bass clef staff notation.
Musical Symbols Reference
A reference guide to standard musical symbols and notation marks.
Who is this for?
- ✓ Pianists and keyboard players studying scales, modes, and chords
- ✓ Guitarists exploring scales and chord voicings across the fretboard
- ✓ Composers and songwriters looking for chord progressions, modulations, and voice leading ideas
- ✓ Music theory students preparing for exams or working through coursework
- ✓ Teachers looking for a visual reference to demonstrate theory concepts in lessons
- ✓ Vocalists and instrumentalists training their ear with interval exercises
- ✓ Music enthusiasts who want to understand the theory behind the music they play or listen to
How musicians use it
Songwriter Finding a Chord Progression in a New Key
A songwriter has been working in C major and wants to try a song in B-flat major. They open Music Theory Companion, select the B-flat major scale, and browse the diatonic seventh chords displayed on the keyboard. They tap through chords until they find a progression that fits the mood, then note the Roman numeral degrees and take the idea back to their instrument.
Guitarist Learning Modes
A guitarist who knows the pentatonic scale wants to understand modes. They open the app, select the Dorian mode for A, and view which notes differ from A natural minor on the fretboard. They tap each note to hear it, then switch to the Circle of Fifths to see how Dorian relates to the other modes of the parent major scale.
Music Student Preparing for an Ear Training Exam
A conservatory student has an ear training exam in two days. They run through the interval ear training exercises focusing on minor 6ths and major 7ths — intervals they consistently miss. After ten minutes they can reliably distinguish both intervals and move on to reviewing their prepared material with the pitch detector.
Composer Using Voice Leading for a Film Cue
A film composer needs a haunting progression that moves away from the tonic without feeling random. They open the Cube Dance tool and map out a path through three chord transformations — Parallel, Leittonwechsel, Relative — arriving at a chord colour that would not appear in a standard diatonic progression but still resolves elegantly.
Teacher Demonstrating Scale-Chord Relationships
A piano teacher opens Music Theory Companion on a tablet during a lesson. They select the D harmonic minor scale and show the student how each diatonic chord is built from scale tones, tapping through the triads on the keyboard display. The student can see and hear how the raised seventh degree creates the characteristic diminished chord on the seventh degree.
Other apps by PG App Studio
Grand Piano and Keyboard
Your full 88-key grand piano with 109 instruments, scales, chords, and a metronome — all on your phone or tablet.
Stage Metronome with Setlist
The stage-ready metronome built for live musicians — with setlist management, precise timing, and a display you can read from across the room.