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Parallel motion of imperfect consonances mostly derive from formulas for improvising music and are often built up in layers, like when, for instance, parallel 6ths between the superius and tenor are combined with alternating 3rds and 5ths between the tenor and bassus. Parallel 3rds or 10ths are often used for shadowing a soggetto involved in imitation, thus introducing homophony in a predominantly polyphonic context.
The main interval patterns described below can be combined with each other and any other musical type.
3-5 Chain
A sequence of alternating 3rds and 5ths between two voices, in any order (3-5 or 5-3). See an Example here.
5-6 Chain
A sequence of alternating 5ths and 6ths between two voices, in any order (5-6 or 6-5). See an Example here.
8-3 Chain
A sequence of alternating octaves and 3rds (or 10ths) between two voices, in any order (8-3 or 3-8). See an Example here.
Parallel 3rds or 10ths
This type of motion can be found in any pair of voices, adjacent or nonadjacent. See an Example here.
Parallel 6ths
This type of motion is more often found between the superius and tenor. See an Example here.
Brief interruptions of a chain or parallel pattern between two voice-parts can occur without breaking the scheme as a whole. In analysis, the intervening voice-parts are marked from top to bottom, as in "ST".