The ChordFinder Java application helps you to find the names of chords that you play on your guitar (or piano).
When I used to be in indie rock bands (e.g. "Vital Items", "Raisin", "Mantazzo", "The Unknown Host", "Minor Problems", sheds tear...) part of the songwriting process would be to try modifications of existing chords, e.g. play a B major on the 7th fret, and play the high b and e strings open. It sounds nice and gritty, but as an autodidact, I wouldn't know what those chords are called. This app helped me with that, i.e. figuring out that the above chord is a B11. Then I would write the chords down on a piece of paper, e.g. Cmaj7, B11, D6*9, and explain to my bandmates, it's just C, B, D on the higher frets, but always play the b and e strings open. In programming, this would be frowned upon as "a workaround" ;-)
There's a manual for the application and also a section about finding chords, i.e. the approach (algorithm) used to determine the chords from the notes.
To run the application, you'll need to install Java (version 11), download the jar file, and run it (on Linux with java -jar ChordFinderApplication.jar, on Windows/Mac by clicking on things).
To compile the code yourself, clone the repo and do:
cd src
javac *.java
java ChordFinderApplication
Or with make:
cd src
make
make run
This code was written around the year 2000 with J2SE 1.2. I don't remember if I was any good at coding then; I dare not look now! Some years later I ported it to J2SE 1.4; the initial commit reflects that state. The subsequent commits are dedicated to porting to SE 11 (16 years forward in half an hour!), fixing linter warnings, and converting the html documentation to markdown.
Probably there are better tools or apps for doing this these days. But this was useful for me at the time, so I thought I'd make it open source, even if it is very old.
ChordFinder is intended to help find the names of chords played on a guitar, bass or piano, as well as alternate positions for this chord. "Playing" chords is done by clicking them in a visualization of the instrument. There is a seperate section on finding chords.
The ChordFinder should be displayed more or less as below. Its three main components are:
- The Instrument Panel, which shows an instrument on which notes are displayed.
- Current Chord Panel. This panel displays the current chord. The name of this chord is in its border, and a representation of this chord below.
- Select Chord Panel. This panel allows you to choose the current chord. It also lists the chords currently played in the instrument.
This panel allows you to "play" notes on an instrument (in green), and visualize notes from the chord in the Chord Panel (in blue). It either displays the fretboard of a guitar, or the keyboard of a piano.
It is important to understand the difference between green and blue notes (pun not intended). Green notes are manually specified through clicking in the Instrument Panel, for instance on the guitar's fretboard, or the piano's keyboard. These notes are "played". Blue notes are not actually played, but are part of the current chord displayed in the Current Chord Panel.
Strings can be strummed by clicking at a fret. The 0th fret is the nut. The number of frets and the tuning can be chosen at the top of this panel. Not strumming a string can be achieved by clicking in the tabs notation to the right of the neck, where right handed guitar players would normally strum. Pressing clear removes any notes played.
Essentially as the guitar panel, but then, well, a piano. The number of octaves displayed can be varied.
The name of the currently selected chord is displayed in this panel's border. In the panel itself, a representation of the chord is shown in two rows of circles. The name of the intervals (1,3,b7,...) are listed above, and the corresponding note (c,c3,d#...) below.
Green circles mean that this note is played in the chord found in the Instrument Panel, and blue means it is not. Red indicates that the note is the bass note (the note with the lowest frequency) being played.
In the example below, the chord Esus4 is displayed. The "e","a","b" notes of this chord are played in the instrument panel, but the "b" is not. The bass note is "a". This corresponds to the note being played in the Instrument Panels abov.e
The "Show chord in instrument" determines whether or not the current chord is displayed in the Instrument Panel.
In this panel, you can choose the current chord. It can be chosen from a list of all chords, or a list of chords that match the notes played in the Instrument Panel.
This panel lists all possible root notes (c..b) and most common chords.
This tab lists the chords that match notes currently played in the Instrument Panel. How these chords are found, and what the checkboxes below this list mean is explained in the next section on the page on finding chords.
This section will probably not make much sense if you have not yet read the page on finding chords, especially the section on filtering chords.
Which chords are listed can be controlled with the check boxes below the list.
- All chords whose notes are a superset of the notes played are listed.
- As 1), but the root note of the chord must be played.
- As 2), but all notes of the chord must be played.
- As 2), and the root note must be the bass note.
To determine which chord belongs to a sequence of notes, we need to know:
- All known chords
- How to match a set of intervals to a known chord
- How to compute a set of intervals given a set of notes and a root note
- How to match a set of notes and a root note to a known chord
With these knowledge many chords will fit a sequence of notes. Therefore, I define some rules with which unlikely candidates can be excluded.
To find the chord played in the Instrument Panel, I first defined a set chords, along with the intervals they contain, as follows:
Name : Intervals Name : Intervals Name : Intervals Name : Intervals
1 : 1 7 : 1 3 5 b7 9 : 1 3 5 b7 9 11 : 1 3 5 b7 9 11
5 : 1 5 m7 : 1 b3 5 b7 m9 : 1 b3 5 b7 9 m11 : 1 b3 5 b7 9 11
major : 1 3 5 maj7 : 1 3 5 7 maj9 : 1 3 5 7 9 maj11 : 1 3 5 7 9 11
m : 1 b3 5 6 : 1 3 5 6 9sus4 : 1 4 5 b7 9 11+ : 1 3 5 b7 9 #11
dim : 1 b3 b5 m6 : 1 b3 5 6 6*9 : 1 3 5 6 9 m11+ : 1 b3 5 b7 9 #11
+5 : 1 3 #5 7sus2 : 1 2 5 b7 m6*9 : 1 b3 5 6 9 13 : 1 3 5 b7 9 11 13
m+5 : 1 b3 #5 7sus4 : 1 4 5 b7 7-9 : 1 3 5 b7 b9 m13 : 1 b3 5 b7 9 11 13
sus2 : 1 2 5 7-5 : 1 3 b5 b7 m7-9 : 1 b3 5 b7 b9
sus4 : 1 4 5 m7-5 : 1 b3 b5 b7 7-10 : 1 3 5 b7 b10
7+5 : 1 3 #5 b7 9+5 : 1 b7 b9
m7+5 : 1 b3 #5 b7 m9+5 : 1 b7 9
7+5-9 : 1 3 #5 b7 b9
m7+5-9 : 1 b3 #5 b7 b9
It is easier to store these intervals as semitone distances to the root
note. For instance, the semitone distances of the minor chord are
(1-1, b3-1, 5-1) = (0 3 7). The list of known chords is actually stored as follows:
Name : Intervals Name : Intervals Name : Intervals Name : Intervals
1 : 0 7 : 0 4 7 10 9 : 0 4 7 10 14 11 : 0 4 7 10 14 17
5 : 0 7 m7 : 0 3 7 10 m9 : 0 3 7 10 14 m11 : 0 3 7 10 14 17
major : 0 4 7 maj7 : 0 4 7 11 maj9 : 0 4 7 11 14 maj11 : 0 4 7 11 14 17
m : 0 3 7 6 : 0 4 7 9 9sus4 : 0 5 7 10 14 11+ : 0 4 7 10 14 18
dim : 0 3 6 m6 : 0 3 7 9 6*9 : 0 4 7 9 14 m11+ : 0 3 7 10 14 18
+5 : 0 4 8 7sus2 : 0 2 7 10 m6*9 : 0 3 7 9 14 13 : 0 4 7 10 14 17 21
m+5 : 0 3 8 7sus4 : 0 5 7 10 7-9 : 0 4 7 10 13 m13 : 0 3 7 10 14 17 21
sus2 : 0 2 7 7-5 : 0 4 6 10 m7-9 : 0 3 7 10 13
sus4 : 0 5 7 m7-5 : 0 3 6 10 7-10 : 0 4 7 10 15
7+5 : 0 4 8 10 9+5 : 0 10 13
m7+5 : 0 3 8 10 m9+5 : 0 10 14
7+5-9 : 0 4 8 10 13
m7+5-9 : 0 3 8 10 13
Given a set of intervals (for instance (0 5 10) = (1 4 b7)) it is now
possible to compute which chord this might be. I simply compare these
intervals to those in the table of known chords. If each given interval
is also in the list of intervals of a known chord, it might be this
chord. Given (0 5 10), the possible chords are therefore
7sus4 : 0 5 7 10 and 9sus4 : 0 5 7 10 14. Although both chords
contain all the given intervals, it doesn't make much sense to choose
9sus4. The "best chord" for a given set of intervals is defined as the
possible chord with the lowest index in the table above.
Suppose we have the notes (e,a,d) and want to know the intervals,
given the root note e. This is done my measuring the distance, in
semitones, between each note and the root note. For this example, this
yields (e-e,a-e,d-e) = (0 4 10). As we saw, the best chord for this
set of intervals is 7sus4. Because the root note is e, we therfore
know it is a E7sus4 chord.
We now know how to match intervals to a known chord, and also how to
compute intervals given a set of notes and a root note. Therefore, we
can also match a set of notes and a root note to a known chord. Suppose
we have the notes (a# c d f d# g) and specify that the root note is
c. First we compute the intervals given the root note
(a#-c c-c d-c f-c d#-c g-c) = (10 0 2 5 3 7). Unfortunately, there is
no known chord with the intervals ( 0 2 3 5 7 10). The reason is that
when computing the intervals of a set of notes, the interval can never
become larger than 11 semitones. For example
a#-c=10, b-c=11, c-c=0, c#-c=1. Therefore the intervals of the known
chords should also be confined to the range [0-11]. For instance the
chord m11 : 0 3 7 10 14 17 is converted to m11 : 0 3 7 10 2 5. This
does correspong to the intervals (10 0 2 5 3 7). Therefore, the
notes (a# c d f d# g) with root note c correspond to a Cm11 chord.
What if the root note is unknown? The procedure is to simply try each
note c..b as a root note, compute the intervals, and match the best
chord. For the notes (a d e).
Root note : Intervals = Known chord (intervals) CAI RNP ANP R=B
a d e
c : 9 2 4 = C6*9 (0 4 7 9! 14=2!) Y
c# : 8 1 3 = C#m7+5-9 (0 3! 8! 10 13=1!) Y
d : 7 0 2 = Dsus2 (0! 2! 7!) Y Y Y
d# : 6 11 1 = X
e : 5 10 0 = E7sus4 (0! 5! 7 10!) Y Y
f : 4 9 11 = X
f# : 3 8 10 = F#m7+5 (0 3! 8! 10!) Y
g : 2 7 9 = G6*9 (0 4 7! 9! 14=2!) Y
g# : 1 6 8 = X
a : 0 5 7 = Asus4 (0! 5! 7!) Y Y Y Y
a# : 11 4 6 = X
b : 10 3 5 = Bm11 (0 3! 7 10! 14=2 17=5!) Y
An X means that now known chord contains all given intervals. So,
given the notes (a d e), the possible chords are C6*9, C#m7+5-9,
Dsus2, E7sus4, F#m7+5, G6*9, Asus4, Bm11. Their intervals are also
listed. An exclamation mark means this interval is actually played.
[]{#filteringchords}
The list above shows the naivety of the procedure: no mucisian would
call (a d e) a Bm11. The root note and fifth aren't even played! It
is simply included, because Bm11 contains the intervals 10 3 5.
Therefore, several "filters"/"rules" should be applied. These are
liste below. Which chords conform to the rules is depicted in the table
above.
- Contains all intervals (CAI). This rule says that all the given intervals must be contained in the intervals of the known chord. This is actually not a filter at all. It is basically the main rule for finding chords in the first place.
- Root note played (RNP). This rule says the root note must be played. Applying it already removes most chords. Only Dsus2, E7sus4, and Asus4 remain. It can easily be read from the intervals: they must contain 0.
- All notes played (ANP). This rule says all the notes in the chord must be played. This does not hold for E7sus4, because the fifth is not played. It can easily be read from the intervals, which must contain as many notes as the intervals of the known chord.
- Root note is base note (R=B). This rule says that the lowest note (the first in the set) must be the root note. This only holds for Asus4. It can easily be read from the intervals: the first interval should be 0. This rule is very restrictive: theoretically, this rule holds for at most one chord.