Hi there, C1-B2 are off limits unfortunately, they are designated by default to play the full loop as is sliced, however, at different keys for pitch differences. If you have the randomize function enabled, these keys will also play that pattern, as set. These keys are shown in light green for this reason. The keys in white are your actual slices. Dragging and dropping the midi pattern from the slice player also automatically assigns the slices starting at C3.