Advanced question: Why exactly is a C major chord not a triad?
The well-known musicologist Carl Dahlhaus has offered a very sensible, but also astute definition of the concept of chords for tonal music:
›Akkord‹ wurde ursprünglich der bloße Zusammenklang verschiedener Töne bezeichnet. In der Theorie der tonalen Harmonik aber werden erstens nur drei- oder mehrtönige Zusammenklänge als Akkorde bezeichnet, zweitens die zweitönigen Zusammenklänge als Fragmente von drei- oder viertönigen interpretiert, drittens die Akkorde nicht als Resultate, als Zusammensetzungen von Tönen und Intervallen, sondern als unmittelbar gegebene Einheiten aufgefaßt und viertens die Abstände zwischen den Grund- oder Bezugstönen der Akkorde als Kriterium der Klangverbindungen betrachtet.
Carl Dahlhaus, Untersuchungen über die Entstehung der harmonischen Tonalität, Kassel 1968, S. 57.
Attempt at translation: The term ›chord‹ was originally used to describe the sound of different tones played at the same time. In the theory of tonal harmony, however, firstly, only three- or multi-tone combinations are called chords, secondly, the two-tone combinations are interpreted as fragments of three- or four-tone ones, thirdly, the chords are not understood as results, as combinations of tones and intervals, but as directly given units, and fourthly, the distances between the fundamental or reference tones of the chords are regarded as the criterion of the sound combinations.
Thinking a bit about this sentence (which is a bit long and complicated) is worth it. Dahlhaus says:
- All possible tones that sounded together (so, for example, also the tones c-e-g) used to be called chord.
- Today, combinations of three or more tones are called chords when we think of these tones as an immediate unit that has a root (as in the video, where the tones c-e-g were discussed as major and minor chords with the root c).
- We even hear thirds as chords (rather than intervals) in this sense. For example, we can hear c-e or e-c as a C major chord without the fifth g (try it on the piano, it really works!).
- We can recognize a chord progression by the relation of its root notes (and the rules by which certain chord progressions sound good is what so-called harmony attempts to describe).
So, why is it now inaccurate when we speak of a C major triad?
If one speaks of a C major triad, then one has recognized c as the root of a chord (because only then one can speak of a C major at all). This means that you no longer hear three individual tones c, e and g and neither two thirds or intervals c-e and e-g, but a unit (major) with a fundamental c. And exactly then, when one recognizes this unity, it makes sense, according to Dahlhaus, to speak of a chord (and no longer of a triad, in which the three tones would have the same rights and no note is a root).