Key Center

This is a preview of the educational program A Jazz Improvisation Almanac which is under development for the Outside Shore Music Online School. Feel free to browse this preview and learn what you can from it. For a more completed product, though, check out the original freely browsable jazz textbook, A Jazz Improvisation Primer.

As has been mentioned in previous sections, if a piece tends to use notes from a particular scale, the piece is said to be in the key of that scale. For example, here is an F major scale:

[EXAMPLE]

And here is a short piece in the key of F major:

[EXAMPLE]

Normally, this piece would be notated in the key signature of F major:

[EXAMPLE]

The note F, the root of the corresponding scale, is called the tonic of the key. A phrase that uses notes from the corresponding scale exclusively, as the above example did, is referred to as diatonic. Most compositions are not entirely diatonic, even though they may be primarily in one given key. For example, the following piece is in G major, but it contains the note C#, which is not part of the G major scale:

[EXAMPLE]

Why is this piece said to be in G major rather than D major, which contains a C# and therefore would allow the piece to be considered diatonic? The concept of key center goes beyond simply specifying what notes are allowed. The use of the word "center" in the phrase "key center" is significant. The root of the corresponding scale is called the tonic of the key center. This note is the most stable in that key. A phrase can feel complete if it ends on that note. For example, here is a piece that is missing its final note:

[EXAMPLE]

What note would you expect to hear to complete that phrase? If your ear is accustomed to Western harmony, you would presumably expect to hear it complete as follows:

[EXAMPLE]

The different degrees of a scale all provide a different amount of tension with respect to the tonic. Perhaps the most important tension in a major scale is in the seventh degree - the note a half step below the root. This note is referred to as the leading tone, because it leads naturally to the tonic. For example, the following phrase uses the leading tone as the second to last note, and is followed by the tonic:

[EXAMPLE]

It is important to note that the tonic and leading tone can appear anywhere in a phrase, not just at the end:

[EXAMPLE]

It is the ends or cadences of a phrase that are the most important for determining key center, however.

The idea of the tonic is the key (no pun intended) to identifying the key center for a piece in a minor key. Since each minor scale uses the same notes as its relative major, it would be impossible to determine whether a piece were in, for example, G major or E minor, simply by observing what notes are used. By listening to the piece, however, you should be able to identify the tonic as the note on which the piece most wants to end.

Copyright 2000 Outside Shore Music
Authored by Marc Sabatella

Key Center