Fifthwheel

Circle of fifths for key signatures, chords, modes and finding a song's key

Fifthwheel is a working circle of fifths. Tap any key on the wheel and the whole ring turns to bring it to the 12 o'clock position, then read off everything you need to know about that key without leafing through a book.

THE WHEEL Twelve major keys sit on the outer ring and their relative minors on the inner ring. Turn it to any key and see its key signature (the sharps or flats in their proper order), the notes of its scale, its relative and parallel keys, and the two neighboring keys one fifth either side. Tap any related key to jump straight to it. A switch for alternate spellings changes the keys at the bottom of the wheel between B, F sharp and D flat and their enharmonic twins C flat, G flat and C sharp.

CHORDS See the triads and the seventh chords of any major key, natural minor or harmonic minor, with Roman numerals (I ii iii IV V vi vii) and the tonic, subdominant or dominant role of each degree. Step through neighboring keys with the arrows to compare how the chords change.

MODES View the seven modes, Ionian to Locrian, either as the seven modes that share one key signature or as every mode built on the same starting note, each with its notes and its scale formula.

KEY FINDER Enter the chords of a song in order. The app ranks the keys that contain them, shows how each chord is numbered in that key, and flags chords that only exist in harmonic minor. Tap a result to open that key on the wheel.

QUIZ Ten multiple-choice questions per round on key signatures, relative keys and the I, IV and V chords. Your highest score is kept on the device.

GUIDE AND SETTINGS A plain-English guide explains every screen. Settings let you choose the default minor scale for the chord table and reset everything with one confirmation.

Everything runs on your phone. There are no accounts, no ads and no network access, and your selected key, chord list and quiz scores never leave the device. The theory shown is general guidance in standard Western notation.

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