Altered dominant 7th chords

In an altered dominant 7th chord altered tension tones (b9, #9, #11 or b13) are added to the basic chordtones instead of natural tension tones (9, 11* or 13).

*) The 11 (4th) will normally not be added to a V7 chord. If you use a fourth, you will omit the third. The result is a sus4 chord.

• If a dominant 7th chord comes with the ending alt (e.g. G⁷alt), you can decide which alterations you add to the V7 chord.
• The tension tones may be exactly written in the chord symbol, e.g. G^7(b9), G^7(#9), G^7(b13), G^7(b9,b13), etc. if the composer or arranger has intendet to do so or you're dealing with a transcription that just shows what was played on a certain recording.
  Especially in tunes with frequent chord changes (1-2 chords per bar, medium or up tempo) even these chord symbols are often just taken as a common V7alt, which means you may play a G^7(b13) instead of a G^7(b9), because it's more handy to play on the fretboard for the moment.
• Often tensions are not written at all in the chord symbol. The experienced musician will decide by himself to play a G7 as a straight G7 or with a 9 or 13 or as a G7alt, according to the stile of music, melody and the whole chord progression.

If the dominant 7th chord resolves to a chord whose root is a 5th lower (a 4th higher), you can (sometimes even have to) use altered tensions.

Two-Five-One in major

In a 2-5-1 progression in major you can equip the V7 chord with natural tensions as well as altered tensions. Even mixed forms like G^7(b9,13) are possible.

Two-Five-One in minor

In a 2-5-1 in minor you even must use altered tensions. Since the 5th scale degree of minor is equal to the 3rd degree of major, b9 and b13 feel natural, because they are tones that belong to the scale.

Does the V7 chord not resolve from V to I by a 5th, you can add a #11 and/or the natural tensions 9 an 13 to the dominant chord. you can see thet the #11 has kind of an exceptional position and also (or rather) occurs when not in general altered tensions are used.