Major 7th and Seventh Chords

There are two different major chords described as sevenths in the diatonic scale.

 C major 7th or  Cmaj7 and a C seventh or C 7. 

In creating Cmaj7 from the C Major chord we flatten the C one semitone to B.

In creating C7 from the C Major chord we flatten the C two semitones to Bb. 

There can only be one 7th chord that is a Major in the sense of C7 in a key. So that chord will determine the key of the bar

and possibly the piece in which it appears.

There can be more than one  Major 7th chords in a key, as in Cmaj7,Fmaj7. 

The relationship of the notes means that often the scale can contain chords, embellished, with the following attributes.



C Major Chord Progression

C, Dm, Em, Fmajor, G7, Am, Bdim, C

or an embellishment 

Cmaj7, Dm7, Em7, Fmaj7, G7, Am7, B half dim, Cmaj7