>A chromatic mediant relationship is a relationship between

>whose roots are related by a major third or minor third
bad bait

>>73201590
???

The key word here is mediant. Mediants are III chords specifically (III, iii, bIII....), and a chromatic mediant is a case in which two chords (That are a major or minor 3rd apart) contain:

One common tone
One chromatically altered tone

An example being C major and Eb Major

C = C E G
Eb = Eb G Bb

Both chords contain G, and Eb is a chromatic alteration of E. Thus, C major and Eb major are chromatic mediants.

There's also doubly chromatic mediants, where there are two chromatically altered tones and no common tones, such as C major and Eb minor.

>music theory

>>73202946
This. Creep uses a chromatic mediant so that the entire song has a three chromatic note part throughout. It's an I - III - IV - iv progression in G. So the D of the I becomes the Eb of the III which becomes the E of the IV which becomes the Eb of the iv. It the cycles for the entire song. Things like this allow you to use a non diatonic chord progression without it sounding jarring to normie ears.