Second Species in Three Voices
It will be noticed that in Example 8-2 at mm. 5-6 the tenor and bass have parallel octaves on successive downbeats. In three voices the rule against parallel perfect fifths and parallel perfect octaves on successive downbeats has traditionally been relaxed providing: (1) the intervening note is a consonance; (2) an inner voice is involved; (3) the voice in half-notes moves in contrary motion to the voices with whole-notes. Example 8-3 illustrates.