The Measure button lets you automatically restrict the Loop Capture sample length to one, two or four bars, and Auto Start provides level-triggered sampling. Auto Start is really handy for quickly resampling individual pads (perhaps through the effects) and recording D-Beam synth riffs, although it tends to respond a bit late for things like drum loops/hits, even with the lowest level-threshold setting. The Source Select button lets you feed the Loop Capture section just from the mic/line inputs and D-Beam synth, which means that you can record ideas on the fly while pads are being played by the sequencer. Given that the D-Beam synth can't actually be controlled from the internal sequencer at all, Loop Capture is actually the best way to incorporate this in your programmed tracks.

:"...although it tends to respond a bit late for things like drum loops/hits, even with the lowest level-threshold setting."