Explaination of Tonic, Subdomiant and Dominate 7th

[EmmanuelFolo]

Hello guys could someone please explain the following definitions to me and there importance


Tonic, Subdomiant and Dominate 7th


Cheers

Edited November 19, 2007 by EmmanuelFolo

[7string]

The tonic is another name for 'root' or the key that a piece is in.

Subdominant is the name for the 4th note of a major scale as well as the chord built upon this note.

Dominant 7th is the 7th chord built upon the dominant (5th) note of a diatonic scale. In the key of C (or where C is the tonic) the chord is built from G using the same formula as any major or minor triad (root, 3rd & 5th). With 7th that includes F.

The construction of the chord can also be thought of as 1, major 3, perfect 5, flat 7th which starting from G gives B (major 3rd from G), D (perfect 5th from G) and the flat 7th (F).

When you see a chord described as note7 (such as G7) is always means dominant 7 (1, 3, 5, b7).as opposed to major 7, minor 7 or diminished 7.

So in C, the dominant 7th chord is G, B, D and F. This chord has a sound that makes it want to resolves to the tonic chord, so G7 to C major (the leading note B, resolves to C).


Hope this helps !!

Edited November 19, 2007 by 7string

[EmmanuelFolo]

Thank you so much find are alot clearer now cheers

[OutToPlayJazz]

As stated above, every note within any given key has a technical name, as below.

C Major

1st C Tonic
2nd D Supertonic
3rd E Mediant
4th F Sub Dominant
5th G Dominant
6th A Sub Mediant
7th B Leading Note
8th C Tonic (Octave)

These are all the notes in the key of C Major, but every key has the same names attached to it's particular notes, so for example, the sub dominant note in A Major would be D.

The terminology of a "dominant 7th" describes a 7th chord (eg. GBDF in C Maj) based upon the 5th note in the scale of the given key.

As 7string very ably explained, the subdominant is the major chord based upon the 4th note of the scale. (eg. FACF in C Maj.)