Midi Chord Analyser

Features

Common block chords are displayed with their root note, quality and scale degree.

When running the app appears as a midi input device called ChordAnalyser

The app uses Linux ALSA. Jack compatibility may be added later.

Root note:

eg C,C♯,E,E♭ ...

Quality:

eg Major, m Minor, ⁺ Augmented, ° Diminished, ⁷ Seventh ...

Scale Degree in Roman Numerals

eg Major chords : I II III IV VI VII

eg minor chords : i ii iii iv vi vii

Example Key signature and chord display

Key    Key   Scale
Sig    Name  Degree   Chord
1♭     Dm    i        Dm
1♭     Dm    ii       E°
1♭     Dm    III      F
1♭     Dm    IV       G
1♭     Dm    iv       Gm
1♭     Dm    v        Am
1♭     Dm    VI       B♭
1♭     Dm    VII      C

Setting the Key Signature

Set the Key Signature by playing far right hand notes A♯BC together followed by the new scale chord.

Example Key Signature Prompt:

           Chord Analyser


KSig  Major RelMinor  Diatonic Scale
7♭      C♭      A♭    C♭ D♭ E♭ F♭ G♭ A♭ B♭
6♭      G♭      E♭    G♭ A♭ B♭ C♭ D♭ E♭ F
5♭      D♭      B♭    D♭ E♭ F  G♭ A♭ B♭ C
4♭      A♭      F     A♭ B♭ C  D♭ E♭ F  G
3♭      E♭      C     E♭ F  G  A♭ B♭ C  D
2♭      B♭      G     B♭ C  D  E♭ F  G  A
1♭      F       D     F  G  A  B♭ C  D  E
        C       A     C  D  E  F  G  A  B  
1♯      G       E     G  A  B  C  D  E  F♯ 
2♯      D       B     D  E  F♯ G  A  B  C♯ 
3♯      A       F♯    A  B  C♯ D  E  F♯ G♯ 
4♯      E       C♯    E  F♯ G♯ A  B  C♯ D♯ 
5♯      B       G♯    B  C♯ D♯ E  F♯ G♯ A♯ 
6♯      F♯      D♯    F♯ G♯ A♯ B  C♯ D♯ E♯ 
7♯      C♯      A♯    C♯ D♯ E♯ F♯ G♯ A♯ B♯ 

To set the key signature play the major or minor chord of the same name.
Play the root note above♯ or below♭ middle C to select keys with 5-7♯ or 5-7♭

eg: To set Dminor key. On the midi keyboard play top A♯+B+C followed by D+F+A

Ref: https://en.wikipedia.org/wiki/Chord_notation

Building

To compile the app under linux download all the files and compile using make.

 $ make # or edit and run the build script to suit

Using

View the midi devices

 $ qjackctl & # press the graph button

Start a synthesizer

qsynth &

Start the app

./ChordAnalyser  -i 20:0 # connect to keyboard.

The keyboard device number may change.

Connect & disconnect the midi connections in qjackctl if needed

View midi events

midisnoop &

If things are not working as expected, visibility is the key

Errors, omissions and improvements

Please contact the author

Built and tested on Ubuntu Linux 22.04 X86 & ARM versions