All basic chord types can be varied to form altered chords. As shown in previous lessons, the raising and lowering of 3rds and 7ths is common, but other degrees of a chord may also be raised or lowered.
When other degrees (e.g. the 5th, 9th, 11th or 13th) are altered, the chord becomes an altered chord. The most common altered chords involve changes to the 5th and 9th degrees. The name of the chord indicates the alterations, as in the examples below. Chord shapes for all these chords are shown on pages 226 to 228.
There are many more chord types and fingerings in addition to the ones demonstrated in this lesson. For a more in-depth study of extended and altered chords, see Complete Learn to Play Jazz Guitar Manual.