Altered dominants are commonly used in jazz as the 5 chord in a minor 2-5-1 or as a 5th chord in general in a minor jazz progression

eg.


Am7b5 - D7alt - Gmin


An ''altered" dominant means that a dominant chord such as D7 has had it's 5th raised or lowered as well as the 9th raised or lowered.

The scale that the Altered chord comes from is the Super Locrian scale (or altered scale), which is the 7th mode of the melodic minor ascending.

eg. D7alt comes from the Eb melodic minor ascending scale