I'm a guitarist duo-ing with a 'harp' player whose strings all are notes in the key of C.
In other words, the harp player has the notes C D E F G A B available, and no others.
The minor triads available are thus Am Dm Em
We would like to play in (faux) Dm.
That is to say, we want to start and end on Dm, and have Dm feel like home-base.
Since C# is not an available note, he cannot construct an A7 chord to "tonicize" the Dm in the classical way.
So, with Dm the designated home-base, within the limitations noted, what chords and extensions can be used with good aural results to "go away" from and "come back" to Dm so as to produce a satisfying (though admittedly non-standard) feeling of cadence and resolution?