From the Digitakt manual . . .
8.4 MIDI NOTES
Of the 128 notes in the standard MIDI range, Note numbers 0–8 correspond to notes C0 through to G0, the leftmost octave (which is sometimes called C-2–G-2 in certain applications). These notes will trigger the sound of track 1 through track 8, respectively (provided they are set to their default channels 1-8). These notes values map to each of the eight tracks, regardless of which track is active.
MIDI note numbers 12–59 (corresponding to notes C1–B4, the second through to fifth octaves in the MIDI range) will trigger the sound of the active track in any of its 49 chromatic variations (as if played by the [TRIG] keys in CHROMATIC mode, see section below), from lowest to highest pitch.