Sound is at heart full of difference. There is no such thing as a static sound. Even the simplest timbre, a single sine wave without overtones, comes about through differences: the push and pull of air molecules as the soundwave travels through space. More complex sounds are dynamic timbres consisting of many partials that each have an internal life of their own. The norm for sound is not unity, but multiplicity; one single sound contains a world of polyphony within.
A “tone” is a principle of unity that is imposed on a sound. If a sound is tuned to a tone, a certain frequency will stand out as defining its character. When multiple sounds are played together, the organization of their respective timbres will determine to what degree they can fuse and be perceived as one; if the tones of these two sounds are heard to be the same tone, the two sounds are said to form a unison.
When we have a sequence of tones in time with varying durations, we often call such a sequence a melody. This suggests that such a sequence forms a clear unity. However, just as the sounds themselves are multiplicities at heart, the same holds for the sequence itself. Melodies typically contain many sub-melodies and internal counterpoints. Local top notes within a melodic line form a sub-melody, and the same is true for bottom notes, and there can be many other types of sub-lines hiding within what seems like one melody. Musicians often play with this principle, famously employed by baroque composers like Bach in their works for solo melody instruments. A single melody contains a world of polyphony within.
What then allows us to speak of “a melody”, when everything in music is multiplicity at heart? It is the recognition that one can find a single strand going through all the levels of movement within sounds and between sounds. One sweep of energy, one gestural motion, weaves its way through the many-tiered play of vibrations and lines, and it is possible for more than one performer to share in this one and same gesture. To recognize a melody as one is to recognize a unity of movement, and this recognition allows different voices to do the same thing.
What happens when two voices share the same movement is very powerful. The voices are different at heart, coming from different sounding bodies and possessing different characteristics, yet when they perform the same melody – when they perform a consistent unison throughout – they share the execution of the same gesture, and this relates them in a meaningful way. Within this relation, each unique sonic identity contributes something to a whole, showing the power of the unifying gesture to contain worlds of difference, and the power of these differences to engender a rich whole.
A choir is not just a single voice multiplied, a violin section is not just a louder violin. The contributions of each of the voices produces a new timbre, as minute differences in individual timbres smoothen out into a powerful new sound. Psychoacoustics calls this the ‘rough tone’ of the ‘chorus effect’.
But the effect of powerful richness in a whole of differences is at its strongest in musical situations that allow each of the voices to retain its own-ness within the whole, such as in heterophonic music, where each voice is allowed a certain freedom when playing the same gesture, producing a richer whole. This one typically finds in middle eastern musical traditions, but one can also think of Giacinto Scelsi’s single-tone pieces for orchestra and John Cage’s ‘unison of differences’ in late orchestral works like Sixty-Eight and Seventy-Four.
In such cases, different voices relate to one another on completely equal footing, and coordinate themselves to produce a gesture that is at the same time powerfully unified and rife with richness and difference. Melody is what allows different voices to participate in the same movement. A unifying principle that allows music’s fundamental differences to collaborate and flourish, as if for the first time.