The document discusses tensions and chord scales in music theory. It defines tensions as extensions of a basic chord that add color and complexity. Available tensions are those that sound acceptable, while harmonic avoid tones are overly dissonant or disrupt chord function. For diatonic major key chords, available tensions are the major 9th above the root. Each diatonic chord has an associated chord scale that identifies its available tensions and harmonic avoid tones. Chromatic tensions can be added to dominant chords to increase instability and drive resolution.