a common method has two parts or movements, subtitled “rock salt” and “quartz”. These two substances are two of the first crystals that were examined by the Braggs using the method of crystallography. Rock salt was one of the first for which they worked out the structure using the method; leading to the ground-breaking observation that rather than pairs of sodium and chloride atoms the structure was made of evenly spaced sodium There are some basic types of material that are shared between the two parts of the piece. The first similarity is a catalogue of chords which are slow transitions from one idea to another, each time changing only slightly. The second similarity is a list of sounds that are made by the singers (the piece has no text) that are further split into voiced and unvoiced sounds. The third similarity are types of events or situations in which a “chord” is sounded by the singers who might perform different types of short or long notes in different combinations. and chloride atoms.

https://research.gold.ac.uk/id/eprint/24851