Kicking over the traces

Text from Foundations Of Practical Harmony And Counterpoint by R. O. Morris, published in 1925:

Appendix II: On Forbidden Consecutives

Those who want to go fully into this difficult, but most suggestive and illuminating problem, should consult Dr. Watt's masterly treatise The Foundations of Music. It is stiff reading, but brings full reward in the end.

Put very briefly, the position as regards prohibited consecutives is as follows:

Consecutive octaves are forbidden, because they are manifestly not true part-writing. One voice that echoes another at an octave distance in not an independent voice at all.

That is because the interval of the octave is so perfect a consonance that the separate identity of the two voices is lost. Even a trained ear, momentarily off its guard, might easily mistake an octave for a single note.

But precisely the same is true of the fifth. The consonance is less perfect, but it is still perfect enough to deceive the untrained ear, which is in fact very liable to mistake the fifth for a single note.

That is, briefly, why classical tradition forbids the use of consecutive fifths and octaves in real part writing (doubling a bass or melody at the octave for purposes of timbre and resonance is of course quite another matter.

So far as it goes, this prohibition is grounded in reason, and in psychological truth.

... [ examples of "bad fifths" and "good fifths" using music notation, with discussion ] ...

Modern composers, of course, will not agree to this cavalier treatment of the fifth - nor, for that matter, of the dissonant intervals - 2nds and 7ths. In these last, undoubtedly, there is a refusal to blend, just as in the 5ths there is too great readiness to do so. But to say, therefore (as classical counterpoint did), that these intervals are so disreputable that one cannot enter their society at all without an elaborate ritual of preparation, seems rather pharisaic.

Classical harmony, as will be seen from Part II, Chapter XIII, is built up entirely on this arbitrary segregation of intervals into sheep-intervals (3rds and 6ths), and goat-intervals (2nds, 4ths, 7ths). That is why modern music is kicking over the traces; it is tired of the limited handful of chords permissible under such a system.

What we need is a new system of counterpoint based on realities, and on a more sympathetic understanding of the goat-intervals and their peculiarities. That would eventually give us a new and infinitely supple harmonic system, wide enough and flexible enough for all our needs.

At present there is only harmonic chaos. That is why no text-book of modern harmony can be written as yet, though people are clamouring for it.

The rest of the book deals with rules for the deployment of chords and notes in harmony and counterpoint, and rules lead to algorithms, and that's where I want to go with this.