Music Theory

Each Web App page has a 'Practical Music Theory' pane at the bottom of the page, explaining the music theory concepts applying to that particular page.

This site does not presume to be any kind of authority on music theory.  We simply present the concepts that are relevant to using our site.
For authoritative music theory references, use the links on our Reference pages.

Here are some of the general music theory concepts used throughout this site:


There are 12 unique note names, and a Key Signature for each; each Key Signature can represent a major Key or a minor Key, so there are 24 unique 'Keys'.   (Keys may sometimes go by multiple names... see Enharmonics.  So you may see people (like Victor Wooten) saying there are 30 keys.  This is just another way of looking at it... 6 of those 30 are just different names for the same sets of notes.  

A Key signature defines all the notes in the scale, from A to G, and which of them are sharp or flat.  For example, the key  signature for the Key of G Major defines the G Major Scale as G A B C D E F♯.  (Different note names are used in different parts of the world.  See Note Names, below.)

Chord Construction

Diatonic Chords are made up of notes from the scale.  Most common chords are constructed as a 'stack of thirds'. (A 'third' interval is defined as any note, paired with a note 2-letternames away from it... so, counting from 1, the second note is skipped, and the next note is the 'third'.)  Take the root note as the first, note, then skip the second, and use the third.  Then take the third above that note, and you have a triad of thirds.  Add the third note above those, and you get what's known as a 'Seventh' chord.  (The Root, the third above the root, the third above that - which is a Fifth avove the root), and a third above THAT, which is a Seventh above the root.

Circle of Fifths

The Circle of Fifths has many uses.  It can be used to determine the number of sharps or flats in a Key Signature. It can be used to transpose chords from one Key to another.

It can be used to find the 7 diatonic triads in any Key.   When using the Circle of Fifths in this way, it is common to add an inner ring of notes, to represent the minor keys and minor chords.  This makes it easier to see the 3 major and 3 minor diatonic chords grouped closely together. (The diminished chord is less common, and is sometimes not labeled on this type of chart.)   

Note Names

Note naming conventions vary around the world.

The note Naming System for each country is generally also used for naming chords (chord symbols), such as a Do chord or a Sol7 chord.