In chords of four-part harmony, three instruments of the same timbre should be combined with a fourth instrument of another:
Harmony in several parts.
In writing chords of 5, 6, 7 and 8 part-harmony, whether they are independent, or constitute the harmonic basis, the student should follow the principles outlined in the [previous chapter], dealing with the progression of wood-wind instruments in octaves. As the 5th, 6th, 7th and 8th notes are only duplications in octaves of lower notes of the real harmony (in 4 parts), instruments should be chosen which combine amongst themselves to give the best octaves. The process of crossing and enclosure of parts may also be used.
A. Wood-wind in pairs (close distribution):
In widely-divided harmony chords in several parts are to be avoided as they will entail both close and extended writing:
