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Music theory tools

Scales and modes in any key, diatonic chords with Roman numerals, a chord transposer, guitar capo calculator, circle of fifths, an interval ear trainer and note / frequency / MIDI / cents conversion.

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Letters are spelled by standard theory (for example G# major contains F##, written "F##"). Use # for sharp and b for flat. Middle C = MIDI 60 = C4 here (some software calls it C3).

Scale and chord explorer

Key (root)

Scale

Chord spelling

Root

Chord type

Transpose a chord progression

Chords (separate with spaces or bar lines; other words are left alone)

From key

To key

Result uses flats for target keys F, Bb, Eb, Ab, Db and Gb, sharps otherwise. Slash chords are transposed on both sides.

Guitar capo calculator

Song key (sounding)

Capo fret

Capo	Shapes to play (major key)	Open-friendly?

Chords of the song as written in its sounding key (optional) become these shapes:

Circle of fifths

Click a key. Clockwise is up a fifth (one more sharp or one fewer flat). The keys next to the chosen one are the most closely related.

Interval reference and ear trainer

Semitones	Interval	Above C	Play

Ear trainer: you hear two notes, one after the other, from the root. Pick the interval.

Your answer

Sound starts only when you click. Needs a browser with WebAudio.

Note, frequency, MIDI and cents

MIDI note number

Note name (e.g. A4, C#3)

Frequency, Hz

A4 reference, Hz

Cents between two frequencies

First, Hz

Second, Hz

f = A4 x 2^((n - 69) / 12); n = 69 + 12 x log2(f / A4); cents = 1200 x log2(f2 / f1). 100 cents = one equal-tempered semitone.