I'm writing a clarinet solo with piano accompaniment in B minor. Is is normal to use a D minor chord (or just the first two notes) in classical music (specifically romantic)? I do have a regular chord progression: the D minor would just be a short 'unresolved' part leading into a repetition of the melody.
The move between B minor and D minor is an example of a chord relation known as a "chromatic mediant," and—although it isn't exactly common—it is a regular feature of Romantic-era common-practice music. Two chords are in the chromatic mediant relation if:
- They are the same quality. That is, the two chords are either both minor or both major.
- Their roots are a third apart from each other. Although some theorists distinguish between chords that can be explained by modal mixture and those that can't be, I think it's easier to include both major-third and minor-third root relations.
This means that any major or minor triad has four possible chromatic mediants. Using B minor as an example, the four chromatic mediant chords are: your D minor example, D# minor, G minor and G# minor. One reason this rather spicy chord progression can work well is that the voice leading can be quite smooth. Any chromatic mediant related chords will always have:
- One note that is chromatically altered. In you example, that's the F# turning into F natural.
- One note moving by step. In your example that would be B moving to A.
- And, crucially, one common tone that acts as a sort of glue between the harmonies. In your example that's the D.
I would add that I don't think you should worry too much about whether something is "proper" or not. If you like how something sounds go for it! However, in this case, you are indeed dealing with a relationship that has precedent in the Romantic era. If you want to try a really strange relation, look up the doubly-chromatic mediant!