Diatonic seventh chords with the bass on the low-E string
Diatonic seventh chords with the bass on the A string
Diatonic ninth chords with the bass on the A string
Diatonic ninth chords with the bass on the D string
Five chord forms viewed in the appropriate part have so "wonderful" structure, that while strumming (playing chords on the guitar with a downward or upward sweep of the thumb or of a plectrum), almost all strings can be used. And this is a big advantage of a guitar as an accompanying instrument. Triads and seventh chords have full, rich sound. This strong sound is a result of doubling and trebling of constituent notes.
But when we start to play in a band or ensemble, the same doubling and trebling notes sometimes worsen the group sound. Imagine a situation that you have two guitarists, a bassist, a pianist, a drummer and a vocalist in your group, and all of them play a chord G Major in the accompaniment during the song. Now let's see: even if guitarists play different chord shapes, together they can take five or six note G, plus a pianist will add two or three G and off course a bassist. Generally, the more complex harmonically music is, the worse sound this set of G notes has. It is not to mention the ideal tuning.
To avoid such situations we use so-called arranged chords sometimes these are called blues chords. The essence of the construction of such chords is that these are the same chords, built on the same chord shapes but without doubling and trebling notes. For better mastering of this material, there are given fingerings of four main diatonic seventh and ninth chords and also diatonic sequences in corresponding keys (seventh chords' scales).
It is topical to begin this part with chords which are widely spread in contemporary guitar music especially in certain styles. These are the so-called quartal&quintal chords. These chords related to the arranged ones because all superfluous notes are removed and only the first and the fifth degrees left. The appearance of these chords is closely related to the appearance of the sound amplifying equipment and different effects, guitar processors which change the sound of an instrument. Many effects are based on different modulations, superimpositions, frequency signal cutoffs…etc. Yet music is a "subtle substance", it deals with resonant sound frequencies. There are consonant and dissonant intervals. In the time of Pythagoras and in the Middle Ages the unison, the octave, the fifth and the fourth were referred to consonant intervals, all other intervals considered to be dissonant. In contemporary music both thirds (major and minor) and their inversions minor and major sixths are referred to consonant intervals. Effects used in contemporary music (especially different overdrives) break weak and unstable (in the opinion of the ancients) consonances of both thirds and both sixths. Then these intervals sound wrongly or even falsely.
By this reason quartal&quintal chords are used in contemporary music, these consist of stable consonant intervals. Surely such chords connected with the chord's tonic. These chords also have five diatonic shapes.