Creator here. In general, the samples are automatically selected using a mix of onset detection and audio analysis, giving preference to clips that have a clear musical pitch. I give a brief explanation here: https://citizen-dj.labs.loc.gov/about/#how-do-you-selectcrea... . The sequencer randomly selects 4 of those samples that are sequential in the source audio. You can change them individually by clicking on the track settings button (the mixer icon).
Is there an explanation of how the 4 samples are chosen in remix mode and is there a way to change them individually?