Matching is the process of analyzing a set of notes and deciding what chords they belong to.
Songtrix performs this operation in several areas, including the Guitar Chord and Notes To Chords tools and the Record Chord window.
How It Works
Lets say, for example, that we play the notes G, B and D and we want to know what chord they make.
These three notes are compared against the notes that are produced by all the chord types that Songtrix knows about, using any of the 12 possible root notes. Something like this:
| Am | = A C E | = fail |
| Bbm | = Bb Db F | = fail |
| ... | ||
| G#m | = G# B D# | = fail |
| Amaj | = A C# E | = fail |
| ... | ||
| Fmaj | = F A C | = fail |
| F#maj | = F# A# C# | = fail |
| Gmaj | = G B D | MATCH |
Multiple Matches
Often you will end up with a clear result from the chord matching process, as in the example above for Gmaj. However, you may also find more than one matching chord comes up in the results.
For example, the two chords Em7 (containing E-G-B-D) and G6 (containing G-B-D-E) are made up of the same four notes. If you start with these notes, both chords will be offered as possible matches.
In these cases, the lowest pitched note plays an important role in deciding how to interpret of the notes. If the lowest of the notes is E, then the chord Em7 would usually be chosen.
Missing Notes
If there is no chord which is an exact match for a set of notes, Songtrix can also show inexact matches. These occur where most, but not all, of a chord's notes are present in the set.
For example, the notes C-E-Bb-Db make a great sound together, and are commonly used in rock and jazz, but have no exact matches with any of the standard chord types.
They are actually closest to a C7b9 chord (which consists of C-E-G-Bb-Db), but without the G note, which can be dropped from this chord without greatly altering its sound.
In every chord, there are some notes which really must be present to preserve its distinct character. These are known as required degrees, and are carefully chosen in the standard chord types to give the best results when matching.
Matching Scales
In the same way, a set of notes can be matched to a scale, using the Notes To Scales tool or the Record Scale window.
If you can identify the scale of a melody, it can give you guidance as to which other notes could be used, and which chords might be suitable to provide the harmony.
Songtrix provides a collection of standard scale types that you can use for matching.
