Dim7
A diminished seventh is pretty useful as the phrase can then go off lots of different ways, on account of the chord being a stack of minor thirds. No major third to help indicate anything. There's only three of them (assuming Western 12-tone, etc) as you loop back to the "C E-flat F-sharp A" flavor after the ones that include C-sharp or D. If you're aiming for more consonance sustain and then step into the chord with other voices, e.g. hold C and E-flat from a previous chord then move to include F-sharp and A which aren't really part of C minor. Well maybe the A is if you're running up A B C in that version of a minor key, but F-sharp A probably moreso implies V/V (dominant of the dominant) by way of D F-Sharp A which is the dominant of G B D which is the dominant of the tonic C E-flat G. Or in other words part of the C-minor tonic glued together with part of the G-something Dominant, if you're thinking harmonically, but you could also take a horizontal view where two or more of the notes just accidentally form a diminished seventh on their way to and from elsewhere.
Another trick used here is to delay some notes a wee bit, which if not overdone will seem to draw out or slow down a phrase. Easy to do on a piano, while in a DAW you might have to fight with the software that's forever snapping the notes to a grid. Some DAW do have a "swing" knob to fiddle with, but that might apply to the whole pattern or phrase, not just that one note.
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