Dvorak’s The Jacobin and Gluck’s Orfeo ed Euridice, the two operas that opened this year’s Buxton Festival, are both relative rarities today, but their creators’ fortunes tell an interesting story. Dvorak’s operas — or at least Rusalka — joined the repertoire around the same time, during the 1980s, that Gluck’s arguably starting slipping from the stage, to the extent that now means the UK’s main companies are all but ignoring the composer’s 300th anniversary this year.