Now in its sixth year, the Australian Haydn Ensemble has become something of a jewel in the national period instrument crown. A reputation for intriguing programming of the unfamiliar (or in this case the downright obscure) alongside better known fare makes an AHE concert one of the more pleasant ways to pass a sultry Sydney Sunday afternoon. Of course, one man’s meat is another man’s poison, and while sultry is perfect for conjuring the nocturnal atmosphere for Boccherini’s Madrid, it can play the very devil with gut strings. The result required increasingly frequent judicious retuning between movements, but skilful and sensitive playing on the part of all five players (Skye McIntosh and Caroline Hopson on violins, James Eccles on viola, and Anton Baba and Daniel Yeadon on cellos) ensured nothing too serious ever seemed amiss in an attractively diverse programme of works for string quintet. The opener was one of Mozart’s lesser-known works, an arrangement of his Fantasy in F Minor for Mechanical Organ. Commissioned by a dilettante Viennese impresario to accompany a sort of cabinet of artistic curiosities, Anthony Albrecht’s excellent programme notes speculate that the organ in question was originally meant to complement an effigy of Field Marshall…