In jazz music, the altered scale and it’s appropriate scale is a great choice for melodies and chord voicings to make dominant chords sound full of color and tension. Then resolving that tension into the next chord can sound very pleasing. The scale contains every possible altered tension which are b9, #9, #11, b13 as well as the major 3rd and minor 7th. Here is the scale written out for an altered C7 chord:
This scale is a great option when playing dominant V7 chords that resolve down a fifth to a minor chord such as C7 to a F-7. When resolving down a fifth to a major chord, it is more “normal” to use a natural 13 which corresponds to the major 3rd of the major chord.
Another option is to begin the voicing or melody on a basic mixolydian scale and then switch to the altered scale to finish it. This works well when the dominant chord is a full measure or 2 measures.
It’s worth noting that this scale interestingly has the same notes as it’s relative substitute dominant chord. So in the above example of a C7alt, it shares the same notes as a Gb7 with a #11. These two chords are practically interchangeable because the main difference is the bass note.
Another nice use of an altered chord/scale is resolving it up a half step to a major7 chord. This works because it has the same notes as the IV7 #11 in that major key. So in our C7 example, if it resolves up to a Dbmaj7, it shares the notes of a Gb7#11. This is a great technique if you want to add more chords to a chord progression: slip in the altered dominant chord a half step below the major chord you’re about to play. I specifically use the voicing 3, b13, b7, #9 most often in this situation but feel free to explore your own artistic voicings.
Anyway hope you’ve learned more about the altered dominant chord and scale and a few of it’s various uses.
from the Jazz Ressources