Revelator SpectroChord V1.0 Ó2003

 R.F. La Fontaine

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In essence, SpectroChord V1.0 is a chord identifier for up to five musical notes played simultaneously or in quick succession. It produces a spectrographic display that shows the association between the notes and each of one hundred and thirty two common chords. It saves the user considerable time spent searching tables of chords when seeking that illusive match. SpectroChord has run successfully under Windows 95, 98 and XP.

Chord recognition

How many chords should SpectroChord recognise? Potentially there are thousands of chords, but many musicians agree that, to Western ears, the triads and triads with added sixths, sevenths and ninths encompass the most useful. These may be subdivided into minor, major, augmented, diminished and dominant varieties as appropriate, yielding eleven chord classes:- Minor, Major, Augmented, Minor 6th, Major 6th, Diminished 7th, Minor 7th, Dominant 7th, Major 7th, Dominant Minor 9th and Dominant 9th. A complete chord name also requires the tonic, or key-note name of which there are twelve (A - G#). The products of key and chord class are 132 named chords, all recognised by SpectroChord.

The displayed spectrograph

SpectroChord gradates chords two ways; the first is by key-note (e.g. F#) with the chord classes appended as subdivisions; the second by chord class with keys as subdivisions. Ultimately both methods reveal the same information, but each convey different interesting impressions.

The order of chord classification adopted by SpectroChord depends on the relative positions of the key and its chord elements. Using the minor chord as an example; its elements are located nearest the key-note (the first note of the chord); the second note being three semitones above; the third at seven semitones above the key-note. This arrangement expressed as a binary number is 10,001,001 which equates to the octal number 211, whereas for the major chord it is 221. The numerical order of the eleven chord classes is shown below. The corresponding decimal identity is 137 for the minor chord,145 for the major chord, and 17553 for the dominant 9th. Decimal numbers offer little clues to chord construction so are not included in the table.

Octal Ident Chord Class
00211 minor

00221 major

00421 augmented

01111 diminished 7th

01211 minor 6th

01221 major 6th

02211 minor 7th

02221 dominant 7th

04221 major 7th

22221 dominant minor 9th

42221 dominant 9th

The '1' in the least significant digit of each number represents the tonic. A surprise, perhaps, is the position relegated to the diminished 7th which is usually documented alongside the other sevenths. However, here it is aptly located because of its mathematical relevance.

Data entry

Data are entered through the keyboard using letters A through G in upper or lower case to specify the note names. A note letter can be followed by the symbols # and % (percentage symbol) which sharpen or flatten the preceding note. As examples, f# and e% specify 'F sharp' and 'E flat'. Notes can appear in any order, and space characters can be inserted anywhere. Double flats and double sharps are invalid. Duplicated notes and excess of five notes are ignored. Click the Enter button on the screen to produce the spectrograph.

Spectrograph interpretation

When the xKey button is clicked, chord grouping is by tonic with subdivisions of chord class. Annotation on the vertical axis provides a degree of exactness between the given notes and a chord. The right hand side shows the number of notes matching those of a chord represented by a spectral spike. Given notes A B C D E, the graph shows these include four of the five notes forming a 'D dominant 9th' chord. Not a perfect match - a near hit, maybe. The same note combination has three out five notes correct for twenty-two other chords - all weak fits, perhaps some sounding better than others in particular applications. The spike name is displayed by clicking near its peak. Spikes are closely spaced on the screen, so it is easy to click the wrong one unintentionally. Therefore it is advisable always to compare the color of the spike against that shown beside the displayed chord name. Augmented chords produce three full height spectral spikes; try A% C E for example: here, peaks shown on the spectrograph occur at C E G#. 'A-flat' becomes the enharmonic G# because SpectroChord indicates all half-notes using a sharp '#' designation.

Viewing the help file

You are now looking at the "Help" file which is a HTML document. The default HTML reader is "\windows\explorer". If you need to change this, edit file HtmlReader.txt and change it to indicate the HTML reader you prefer.

Revelator SpectroChord V1.0 is free of charge, makes no registry entries, has no expiry date, and certification that it is free of malware content.  It is subject to a License Agreement which is shown below. 

License Agreement

If you do not agree with all conditions given above, or there are legal concerns regarding the License Agreement presented here that may apply in your state, territory, or situation then you are not licensed to use this software.

<— Visit Softpedia to view SpectroChord's CLEAN certification, issued 27          December 2007.

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