Altered dominant chords are used to bring tension and an outside flavor to jazz chord progressions. They generally resolved to an inside chord as the I or a substitute as iii or vi. They have one or more notes lowered or raised by a half-step, in other words they contain one or more alterations. These alterations can be b9,#9, b5 (#11) and b13 (#5). Jazz musicians, composers and arrangers used them as substitutions for diatonic chords for adding more dissonance and spice up the harmony. This tutorial provides 25 altered guitar chord shapes to understand how they are constructed and how to play them on guitar.