The altered scale on guitar

The Altered Scale is derived as the seventh mode of the melodic minor scale. It is used over dominant chords where both the fifth and the ninth have been altered, hence the name!

The following example shows the seventh mode of Db melodic minor, used over a C7 alt. chord.

From the sixth string, starting with the first finger:

From the sixth string, starting with the fourth finger:

From the fifth string, starting with the first finger:

From the fifth string, starting with the fourth finger: