What are Secondary Mediants / Submediants?

Question

I'm learning about secondary dominants and noticed references to secondary mediants and secondary submediants in a resource (Wikipedia). However, I haven't found any other references to them in internet searches. I think I could guess at the function of these types of chords but the lack of information leaves me wondering if they really exist in the lexicon of music theory. I also wonder if there isn't a different and more practical explanation for whatever function secondary mediants and submediants might play. Can anyone offer any clarity here?

Answer 1

This is an excellent observation! I would argue that the word "secondary" should be seen as "temporary" without the express intent of modulation.

As for the function of these mediants and submediants, (depending on the context of course!) they could be used as either substitutions of V and ii respectively depending on the context or an elongation of the secondary harmony as a "temporary key".

Very interesting question! Please update us on any findings! :-)