A Macro-harmonic Key to Keys
The idea of music being “in a key” can be troublesome. One of the biggest hurdles I see students of music come up against is the presence of “different keys” in a piece “in a key”. Frankly, I can see their point!
It might be better to think in terms of what Dmitri Tymoczko calls “macro-harmonies” in A Geometry of Music:
In most Western and non-Western music, pitches are drawn from a relatively small reservoir of available notes—typically, between five and eight. As a result, Western music has a two-tiered harmonic consistency: at the local (or instantaneous) level… while over larger time spans it articulates a scale by using only seven different notes. The scale can be considered a kind of “large” or macro harmony that subsumes the individual chords.
In other words, instead of “closely related keys”, we might think of “closely related macro harmonies” that differ by only one or two pitches. A useful chart could be made that shows not only what keys are closely related, but also which pitch(es) must be altered to transform one into another. This would show the various accidentals that we would not only accept, but would actually expect in a piece said to be “in a key”.
If not only to simply correct our expectations, this kind of thinking can help us see big-picture relationships in music. The forms of Classical music can sometimes just ‘pop’ off the page when considered in these terms. We can scan a score for the presence of persistent accidentals (i.e., those that are not immediately changed back within a measure or so) to identify global harmonic motion. Take Haydn’s Piano Sonata no. 6 in C major as an example.
In the first block (up to the repeat sign in the score) there are two distinct macro-harmonies: tonic and dominant. The second block (following the repeat sign) has a jumble of several distinct macro-harmonies that last for only a few measures at a time, indicating development or transition. The last block is the longest block of all: a tonic macro-harmony. What kind of form has two contrasting key areas followed by a section that cycles through a number of keys only to settle back into the tonic for the remainder? How about a sonata? (I’ll grant that this is a fairly straight-forward example, but go ahead and try it on other Classical scores; I think you’ll be met with similar success.)
I’ve found this to be useful for some of my students; what do you think?