2. A ______ consists of two or more triads, 7th chords, or other chords sounded simultaneously and spaced far enough apart to make each recognizable as a separate structure. Two triads containing common tones and spaced a distance apart may not be perceived as separate structures if the combination of the two forms a chord very familiar to us. But if the triads contain no common tones and are of suffi ciently contrasting nature, fusion will not result, and each triad will maintain its identity. _______ 內指的什麼？請以中文或英文作答