Dear Bingley: what was this thing called "sambuca"?
"At the engine that Marcellus brought upon the bridge of ships, which was called Sambuca from some resemblance it had to an instrument of music, while it was as yet approaching the wall, there was discharged a piece of a rock of ten talents' weight, then a second and a third, which, striking upon it with immense force and with a noise like thunder, broke all its foundation to pieces, shook out all its fastenings, and completely dislodged it from the bridge."

So I'll go searching for it.Oh, happy day, I found it.
The site shows what looks like a very big harp. But here is what it said about naval siege engine:
"Sambuca was also the name of a military engine, used to scale the walls and towers of besieged cities. It was called by this name on account of its general resemblance to the form of the harp. Accordingly, we may conceive an idea of its construction by turning to the woodcut and supposing a mast or upright pole to be elevated in the place of the longest strings, and to have at its summit an apparatus of pulleys, from which ropes proceed in the direction of the top of the harp. We must suppose a strong ladder, 4 feet wide, and guarded at the sides with palisades, to occupy the place of the sounding-board, and to be capable of being lowered or raised at pleasure by means of the ropes and pulleys. At the siege of Syracuse Marcellus had engines of this description fixed upon vessels, which the rowers moved up to the walls so that the soldiers might enter the city by ascending the ladders (Polyb. viii.5; Plut. Marc. p558, ed. Steph.; Athen. xiv. p634b; Onosandr. Strat. 42; Vitruvius x.16 §9; Festus, s.v. Sambuca; Athen. de Mach. ap. Math. Vet. p7). When an inland city was beleaguered, the Sambuca was mounted upon wheels (Bito, ap. Math. Vet. pp110, 111; Veget. iv.21). "