In music and musical analysis, a subsidiary chord is an elaboration of a principal harmonic chord in a chord progression.

If the principal chord (X) is partially replaced by the subsidiary (Y), there are three possible positions - beginning, middle, and end - for the subsidiary:van der Merwe, Peter (2005). Roots of the Classical: The Popular Origins of Western Music, p.501. . X–Ya Y–X X–Y–X

For example, a subsidiary chord in a modulation.

A subsidiary chord may be a chord with related function and/or sharing pitches, for example in E major, Cm (C-E-G) as a subsidiary for E (E-G-B), which share two of three pitches and are related as tonic parallel (vi) and tonic (I).

See also Parallel key Primary triad

References

Further reading Van der Merwe (2005), p. 428.