Watch the Min. Triad: Alt. Dom. Sound online guitar lesson by Kenny Wessel from Shades of Jazz
Let's continue working with triads over dominant chords, but now we'll look at the minor triad (cousin of major triad, or sibling, I'm not really sure). A minor triad is a root, b3 and 5, the same as a major triad with the third degree lowered by a half step. We can do the same search and discovery process by taking a dominant seventh chord and superimposing all 12 minor triads one at a time to see what colors and tensions are generated. One triad that works really nicely as an altered dominant possibility is the minor triad built a half step up from the root of the dominant seventh chord. For instance, a Db minor triad over a C7 chord gives us these degrees: b9, 3, and b13 (or these pitches: Db, E, Ab). These notes are in the ‘altered' scale and will fit right in with that harmony (the altered scale being the melodic minor scale a half step up from the root of the dominant 7th chord - a very popular altered dominant scale choice).