Strictly speaking, Wikipedia is wrong again. (Surprised?) Steve Knightly plays a large bodied instrument with four courses of unison paired strings, tuned an octave below the mandolin, with the top string tuned down to D. (He sometimes plays in GDAE, and occasionally in ADAD). Tuned like this, the instrument is more properly called an octave mandolin. A true mandocello has much heavier strings (a bass string of around 0.070") and is tuned CGDA, an octave below a mandola. To confuse things even further, some people mistakenly refer to an octave mandolin as a mandola, tenor mandola or octave mandola, all of which it isn't. A mandola is slightly larger than a mandolin, and is tuned a fifth below, i.e. CGDA.